diff --git a/Package.swift b/Package.swift
index 030afe0..f1f6896 100644
--- a/Package.swift
+++ b/Package.swift
@@ -14,7 +14,6 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-algorithms", from: "1.2.0"),
-        .package(path: "./Packages/KissFFT/"),
         .package(path: "./Packages/PFFFT/"),
     ],
     targets: [
diff --git a/Packages/PFFFT/Package.swift b/Packages/PFFFT/Package.swift
index 051cf1a..dce638b 100644
--- a/Packages/PFFFT/Package.swift
+++ b/Packages/PFFFT/Package.swift
@@ -6,12 +6,14 @@ import PackageDescription
 let package = Package(
     name: "PFFFT",
     products: [
-        // Products define the executables and libraries a package produces, making them visible to other packages.
         .library(
             name: "PFFFT",
             targets: ["PFFFT", "PFFFTLib"]
         ),
     ],
+    dependencies: [
+        .package(url: "https://github.com/apple/swift-numerics", from: "1.0.0"),
+    ],
     targets: [
         .target(
             name: "PFFFTLib",
@@ -25,7 +27,7 @@ let package = Package(
         ),
         .target(
             name: "PFFFT",
-            dependencies: ["PFFFTLib"]
+            dependencies: ["PFFFTLib", .product(name: "Numerics", package: "swift-numerics")]
         ),
         .testTarget(
             name: "PFFFTTests",
diff --git a/Packages/PFFFT/Sources/PFFFT/Buffer.swift b/Packages/PFFFT/Sources/PFFFT/Buffer.swift
index 2a2aaac..67c1988 100644
--- a/Packages/PFFFT/Sources/PFFFT/Buffer.swift
+++ b/Packages/PFFFT/Sources/PFFFT/Buffer.swift
@@ -1,27 +1,27 @@
 let bufferAlignment = 32
 
 @frozen
-public struct Buffer<Element>: ~Copyable {
-    let buffer: UnsafeMutableBufferPointer<Element>
+public struct Buffer<T>: ~Copyable {
+    let buffer: UnsafeMutableBufferPointer<T>
     var count: Int { buffer.count }
-    var baseAddress: UnsafeMutablePointer<Element> { buffer.baseAddress! }
+    var baseAddress: UnsafeMutablePointer<T> { buffer.baseAddress! }
 
     public init(capacity: Int) {
         buffer = UnsafeMutableRawBufferPointer.allocate(
-            byteCount: MemoryLayout<Element>.stride * capacity,
+            byteCount: MemoryLayout<T>.stride * capacity,
             alignment: bufferAlignment
-        ).bindMemory(to: Element.self)
+        ).bindMemory(to: T.self)
     }
 
     deinit {
         buffer.deallocate()
     }
 
-    public func withUnsafeMutableBufferPointer<R>(_ body: (UnsafeMutableBufferPointer<Element>) throws -> R) rethrows -> R {
+    public func withUnsafeMutableBufferPointer<R>(_ body: (UnsafeMutableBufferPointer<T>) throws -> R) rethrows -> R {
         try body(buffer)
     }
 
-    public func withUnsafeBufferPointer<R>(_ body: (UnsafeBufferPointer<Element>) throws -> R) rethrows -> R {
+    public func withUnsafeBufferPointer<R>(_ body: (UnsafeBufferPointer<T>) throws -> R) rethrows -> R {
         try body(UnsafeBufferPointer(buffer))
     }
 
diff --git a/Packages/PFFFT/Sources/PFFFT/FFT.swift b/Packages/PFFFT/Sources/PFFFT/FFT.swift
new file mode 100644
index 0000000..c832bea
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFT/FFT.swift
@@ -0,0 +1,276 @@
+internal import PFFFTLib
+import ComplexModule
+import RealModule
+
+@frozen
+public enum FFTType {
+    case real
+    case complex
+}
+
+@frozen
+public enum FFTSign: Int {
+    case forward = -1
+    case backward = 1
+}
+
+public enum FFTError: Error {
+    case invalidSize
+}
+
+public protocol FFTElemental {
+    associatedtype ScalarType: FFTScalar
+    associatedtype ComplexType = Complex<ScalarType>
+
+    static func setupPfft(_ n: Int, _ type: FFTType) throws -> OpaquePointer
+    static func pffftMinFftSize(_ type: FFTType) -> Int
+    static func pffftIsValidSize(_ n: Int, _ type: FFTType) -> Bool
+    static func pffftNearestValidSize(_ n: Int, _ type: FFTType, _ higher: Bool) -> Int
+}
+
+public protocol FFTScalar: Real {
+    static func pffftTransformOrdered(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Self>, _ output: UnsafeMutablePointer<Self>, _ work: UnsafeMutablePointer<Self>?, _ dir: FFTSign)
+    static func pffftTransform(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Self>, _ output: UnsafeMutablePointer<Self>, _ work: UnsafeMutablePointer<Self>?, _ dir: FFTSign)
+    static func pffftZreorder(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Self>, _ output: UnsafeMutablePointer<Self>, _ dir: FFTSign)
+    static func pffftZconvolveAccumulate(_ ptr: OpaquePointer, _ dftA: UnsafeMutablePointer<Self>, _ dftB: UnsafeMutablePointer<Self>, _ dftAB: UnsafeMutablePointer<Self>, _ scaling: Self)
+    static func pffftZconvolveNoAccu(_ ptr: OpaquePointer, _ dftA: UnsafeMutablePointer<Self>, _ dftB: UnsafeMutablePointer<Self>, _ dftAB: UnsafeMutablePointer<Self>, _ scaling: Self)
+}
+
+extension Float: FFTScalar {
+    public static func pffftTransformOrdered(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Self>, _ output: UnsafeMutablePointer<Self>, _ work: UnsafeMutablePointer<Self>?, _ dir: FFTSign) {
+        pffft_transform_ordered(ptr, input, output, work, pffft_direction_t(dir))
+    }
+
+    public static func pffftTransform(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Self>, _ output: UnsafeMutablePointer<Self>, _ work: UnsafeMutablePointer<Self>?, _ dir: FFTSign) {
+        pffft_transform(ptr, input, output, work, pffft_direction_t(dir))
+    }
+
+    public static func pffftZreorder(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Self>, _ output: UnsafeMutablePointer<Self>, _ dir: FFTSign) {
+        pffft_zreorder(ptr, input, output, pffft_direction_t(dir))
+    }
+
+    public static func pffftZconvolveAccumulate(_ ptr: OpaquePointer, _ dftA: UnsafeMutablePointer<Self>, _ dftB: UnsafeMutablePointer<Self>, _ dftAB: UnsafeMutablePointer<Self>, _ scaling: Self) {
+        pffft_zconvolve_accumulate(ptr, dftA, dftB, dftAB, scaling)
+    }
+
+    public static func pffftZconvolveNoAccu(_ ptr: OpaquePointer, _ dftA: UnsafeMutablePointer<Self>, _ dftB: UnsafeMutablePointer<Self>, _ dftAB: UnsafeMutablePointer<Self>, _ scaling: Self) {
+        pffft_zconvolve_no_accu(ptr, dftA, dftB, dftAB, scaling)
+    }
+}
+
+extension Double: FFTScalar {
+    public static func pffftTransformOrdered(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Double>, _ output: UnsafeMutablePointer<Double>, _ work: UnsafeMutablePointer<Double>?, _ dir: FFTSign) {
+        pffftd_transform_ordered(ptr, input, output, work, pffft_direction_t(dir))
+    }
+
+    public static func pffftTransform(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Double>, _ output: UnsafeMutablePointer<Double>, _ work: UnsafeMutablePointer<Double>?, _ dir: FFTSign) {
+        pffftd_transform(ptr, input, output, work, pffft_direction_t(dir))
+    }
+
+    public static func pffftZreorder(_ ptr: OpaquePointer, _ input: UnsafeMutablePointer<Double>, _ output: UnsafeMutablePointer<Double>, _ dir: FFTSign) {
+        pffftd_zreorder(ptr, input, output, pffft_direction_t(dir))
+    }
+
+    public static func pffftZconvolveAccumulate(_ ptr: OpaquePointer, _ dftA: UnsafeMutablePointer<Double>, _ dftB: UnsafeMutablePointer<Double>, _ dftAB: UnsafeMutablePointer<Double>, _ scaling: Double) {
+        pffftd_zconvolve_accumulate(ptr, dftA, dftB, dftAB, scaling)
+    }
+
+    public static func pffftZconvolveNoAccu(_ ptr: OpaquePointer, _ dftA: UnsafeMutablePointer<Double>, _ dftB: UnsafeMutablePointer<Double>, _ dftAB: UnsafeMutablePointer<Double>, _ scaling: Double) {
+        pffftd_zconvolve_no_accu(ptr, dftA, dftB, dftAB, scaling)
+    }
+}
+
+extension Complex: FFTElemental where RealType: FFTElemental & FFTScalar {
+    public typealias ScalarType = RealType
+
+    public static func setupPfft(_ n: Int, _: FFTType) throws -> OpaquePointer {
+        return try ScalarType.setupPfft(n, .complex)
+    }
+
+    public static func pffftMinFftSize(_: FFTType) -> Int {
+        return ScalarType.pffftMinFftSize(.complex)
+    }
+
+    public static func pffftIsValidSize(_ n: Int, _: FFTType) -> Bool {
+        return ScalarType.pffftIsValidSize(n, .complex)
+    }
+
+    public static func pffftNearestValidSize(_ n: Int, _: FFTType, _ higher: Bool) -> Int {
+        return ScalarType.pffftNearestValidSize(n, .complex, higher)
+    }
+}
+
+extension Double: FFTElemental {
+    public typealias ScalarType = Double
+
+    public static func setupPfft(_ n: Int, _ type: FFTType) throws -> OpaquePointer {
+        guard let ptr = pffftd_new_setup(Int32(n), pffft_transform_t(type)) else { throw FFTError.invalidSize }
+        return ptr
+    }
+
+    public static func pffftMinFftSize(_ type: FFTType) -> Int {
+        Int(pffftd_min_fft_size(pffft_transform_t(type)))
+    }
+
+    public static func pffftIsValidSize(_ n: Int, _ type: FFTType) -> Bool {
+        pffftd_is_valid_size(Int32(n), pffft_transform_t(type)) != 0
+    }
+
+    public static func pffftNearestValidSize(_ n: Int, _ type: FFTType, _ higher: Bool) -> Int {
+        Int(pffftd_nearest_transform_size(Int32(n), pffft_transform_t(type), higher ? 1 : 0))
+    }
+}
+
+extension Float: FFTElemental {
+    public typealias ScalarType = Float
+
+    public static func setupPfft(_ n: Int, _ type: FFTType) throws -> OpaquePointer {
+        guard let ptr = pffft_new_setup(Int32(n), pffft_transform_t(type)) else { throw FFTError.invalidSize }
+        return ptr
+    }
+
+    public static func pffftMinFftSize(_ type: FFTType) -> Int {
+        Int(pffft_min_fft_size(pffft_transform_t(type)))
+    }
+
+    public static func pffftIsValidSize(_ n: Int, _ type: FFTType) -> Bool {
+        pffft_is_valid_size(Int32(n), pffft_transform_t(type)) != 0
+    }
+
+    public static func pffftNearestValidSize(_ n: Int, _ type: FFTType, _ higher: Bool) -> Int {
+        Int(pffft_nearest_transform_size(Int32(n), pffft_transform_t(type), higher ? 1 : 0))
+    }
+}
+
+public final class FFT<T: FFTElemental> {
+    public typealias ComplexType = T.ComplexType
+    public typealias ScalarType = T.ScalarType
+
+    let ptr: OpaquePointer
+    let n: Int
+    let work: Buffer<ScalarType>?
+
+    /// Initialize the FFT implementation with the given size and type.
+    /// - Parameters:
+    /// - n: The size of the FFT.
+    /// - type: The type of FFT.
+    /// - Throws: `FFTError.invalidSize` if the size is invalid.
+    public init(n: Int) throws {
+        ptr = try T.setupPfft(n, .real)
+        self.n = n
+        let capacity = T.self == Complex<ScalarType>.self ? 2 * n : n
+        work = n > 4096 ? Buffer<ScalarType>(capacity: capacity) : nil
+    }
+
+    public func makeSignalBuffer(extra _: Int = 0) -> Buffer<T> {
+        Buffer(capacity: n)
+    }
+
+    public func makeSpectrumBuffer(extra _: Int = 0) -> Buffer<ComplexType> {
+        Buffer(capacity: n)
+    }
+
+    @inline(__always)
+    func toAddress(_ work: borrowing Buffer<ScalarType>?) -> UnsafeMutablePointer<ScalarType>? {
+        switch work {
+        case let .some(b): return b.baseAddress
+        case .none: return nil
+        }
+    }
+
+    @inline(__always)
+    func rebind<I>(_ buffer: borrowing Buffer<I>) -> UnsafeMutablePointer<ScalarType>! {
+        UnsafeMutableRawBufferPointer(buffer.buffer).bindMemory(to: ScalarType.self).baseAddress
+    }
+
+    @inline(__always)
+    func checkFftBufferCounts(signal: borrowing Buffer<T>, spectrum: borrowing Buffer<ComplexType>) {
+        guard signal.count >= n else {
+            fatalError("signal buffer too small")
+        }
+        guard spectrum.count >= n else {
+            fatalError("spectrum buffer too small")
+        }
+    }
+
+    @inline(__always)
+    func checkFftInternalLayoutBufferCounts(signal: borrowing Buffer<T>, spectrum: borrowing Buffer<ScalarType>) {
+        guard signal.count >= n else {
+            fatalError("signal buffer too small")
+        }
+        guard spectrum.count >= (T.self == Complex<ScalarType>.self ? 2 * n : n) else {
+            fatalError("spectrum buffer too small")
+        }
+    }
+
+    @inline(__always)
+    func checkConvolveBufferCounts(a: borrowing Buffer<ScalarType>, b: borrowing Buffer<ScalarType>, ab: borrowing Buffer<ScalarType>) {
+        let minCount = T.self == Complex<ScalarType>.self ? 2 * n : n
+
+        guard a.count >= minCount else {
+            fatalError("a buffer too small")
+        }
+        guard b.count >= minCount else {
+            fatalError("b buffer too small")
+        }
+        guard ab.count >= minCount else {
+            fatalError("ab buffer too small")
+        }
+    }
+
+    public func forward(signal: borrowing Buffer<T>, spectrum: borrowing Buffer<ComplexType>) {
+        checkFftBufferCounts(signal: signal, spectrum: spectrum)
+        ScalarType.pffftTransformOrdered(ptr, rebind(signal), rebind(spectrum), toAddress(work), .forward)
+    }
+
+    public func inverse(spectrum: borrowing Buffer<ComplexType>, signal: borrowing Buffer<T>) {
+        checkFftBufferCounts(signal: signal, spectrum: spectrum)
+        ScalarType.pffftTransformOrdered(ptr, rebind(spectrum), rebind(signal), toAddress(work), .backward)
+    }
+
+    public func forwardToInternalLayout(signal: borrowing Buffer<T>, spectrum: borrowing Buffer<ScalarType>) {
+        checkFftInternalLayoutBufferCounts(signal: signal, spectrum: spectrum)
+        ScalarType.pffftTransform(ptr, rebind(signal), spectrum.baseAddress, toAddress(work), .forward)
+    }
+
+    public func inverseFromInternalLayout(spectrum: borrowing Buffer<ScalarType>, signal: borrowing Buffer<T>) {
+        checkFftInternalLayoutBufferCounts(signal: signal, spectrum: spectrum)
+        ScalarType.pffftTransform(ptr, spectrum.baseAddress, rebind(signal), toAddress(work), .backward)
+    }
+
+    public func reorder(spectrum: borrowing Buffer<ScalarType>, output: borrowing Buffer<ComplexType>) {
+        guard spectrum.count >= (T.self == Complex<ScalarType>.self ? 2 * n : n) else {
+            fatalError("signal buffer too small")
+        }
+        guard output.count >= n else {
+            fatalError("outputbuffer too small")
+        }
+        ScalarType.pffftZreorder(ptr, spectrum.baseAddress, rebind(output), .forward)
+    }
+
+    public func convolve(dftA: borrowing Buffer<ScalarType>, dftB: borrowing Buffer<ScalarType>, dftAB: borrowing Buffer<ScalarType>, scaling: ScalarType) {
+        checkConvolveBufferCounts(a: dftA, b: dftB, ab: dftAB)
+        ScalarType.pffftZconvolveNoAccu(ptr, dftA.baseAddress, dftB.baseAddress, dftAB.baseAddress, scaling)
+    }
+
+    public func convolveAccumulate(dftA: borrowing Buffer<ScalarType>, dftB: borrowing Buffer<ScalarType>, dftAB: borrowing Buffer<ScalarType>, scaling: ScalarType) {
+        checkConvolveBufferCounts(a: dftA, b: dftB, ab: dftAB)
+        ScalarType.pffftZconvolveAccumulate(ptr, dftA.baseAddress, dftB.baseAddress, dftAB.baseAddress, scaling)
+    }
+
+    public static func minFftSize() -> Int {
+        T.pffftMinFftSize(.real)
+    }
+
+    public static func isValidSize(_ n: Int) -> Bool {
+        T.pffftIsValidSize(n, .real)
+    }
+
+    public static func nearestValidSize(_ n: Int, higher: Bool) -> Int {
+        T.pffftNearestValidSize(n, .real, higher)
+    }
+
+    deinit {
+        pffftd_destroy_setup(ptr)
+    }
+}
diff --git a/Packages/PFFFT/Sources/PFFFT/FFTDouble.swift b/Packages/PFFFT/Sources/PFFFT/FFTDouble.swift
deleted file mode 100644
index 7b2699e..0000000
--- a/Packages/PFFFT/Sources/PFFFT/FFTDouble.swift
+++ /dev/null
@@ -1,94 +0,0 @@
-internal import PFFFTLib
-
-public final class FFTDouble: PFFFTProtocol {
-    let ptr: OpaquePointer
-    let n: Int
-    let type: FFTType
-
-    static let sharedCache = SetupCache<Element>()
-
-    public static func setup(for n: Int, type: FFTType) throws -> FFTDouble {
-        try sharedCache.get(for: n, type: type)
-    }
-
-    public init(n: Int, type: FFTType) throws {
-        guard let ptr = pffftd_new_setup(Int32(n), pffft_transform_t(type)) else { throw FFTError.invalidSize }
-        self.ptr = ptr
-        self.n = n
-        self.type = type
-    }
-
-
-    func transform(_ input: borrowing Buffer<Element>, _ output: borrowing Buffer<Element>, _ work: borrowing Buffer<Element>?, _ dir: pffft_direction_t) {
-        checkFftBufferCounts(n: n, type: type, input: input, output: output, work: work)
-
-        let workAddress: UnsafeMutablePointer<Element>! = switch work {
-        case let .some(b): b.baseAddress
-        case .none: nil
-        }
-        pffftd_transform_ordered(ptr, input.baseAddress, output.baseAddress, workAddress, dir)
-    }
-
-    func transformUnordered(_ input: borrowing Buffer<Double>, _ output: borrowing Buffer<Double>, _ work: borrowing Buffer<Double>?, _ dir: pffft_direction_t) {
-        checkFftBufferCounts(n: n, type: type, input: input, output: output, work: work)
-
-        let workAddress: UnsafeMutablePointer<Double>! = switch work {
-        case let .some(b): b.baseAddress
-        case .none: nil
-        }
-        pffftd_transform(ptr, input.baseAddress, output.baseAddress, workAddress, dir)
-    }
-
-
-    public func forward(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, work: borrowing Buffer<Double>?) {
-        transform(input, output, work, PFFFT_FORWARD)
-    }
-
-    public func inverse(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, work: borrowing Buffer<Double>?) {
-        transform(input, output, work, PFFFT_BACKWARD)
-    }
-
-    public func forwardUnordered(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, work: borrowing Buffer<Double>?) {
-        transformUnordered(input, output, work, PFFFT_FORWARD)
-    }
-
-    public func inverseUnordered(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, work: borrowing Buffer<Double>?) {
-        transformUnordered(input, output, work, PFFFT_BACKWARD)
-    }
-
-
-    public func reorderSpectrum(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>) {
-        checkFftBufferCounts(n: n, type: type, input: input, output: output, work: nil)
-        pffftd_zreorder(ptr, input.baseAddress, output.baseAddress, PFFFT_FORWARD)
-    }
-
-    public func convolveAccumulate(dftA: borrowing Buffer<Double>, dftB: borrowing Buffer<Double>, dftAB: borrowing Buffer<Double>, scaling: Double) {
-        checkConvolveBufferCounts(n: n, type: type, a: dftA, b: dftB, ab: dftAB)
-        pffftd_zconvolve_accumulate(ptr, dftA.baseAddress, dftB.baseAddress, dftAB.baseAddress, scaling)
-    }
-
-    public func convolve(dftA: borrowing Buffer<Double>, dftB: borrowing Buffer<Double>, dftAB: borrowing Buffer<Double>, scaling: Double) {
-        checkConvolveBufferCounts(n: n, type: type, a: dftA, b: dftB, ab: dftAB)
-        pffftd_zconvolve_no_accu(ptr, dftA.baseAddress, dftB.baseAddress, dftAB.baseAddress, scaling)
-    }
-
-    public static func minFftSize(for type: FFTType) -> Int {
-        Int(pffftd_min_fft_size(pffft_transform_t(type)))
-    }
-
-    public static func isValidSize(_ n: Int, for type: FFTType) -> Bool {
-        pffftd_is_valid_size(Int32(n), pffft_transform_t(type)) != 0
-    }
-
-    public static func nearestValidSize(_ n: Int, for type: FFTType, higher: Bool) -> Int {
-        Int(pffftd_nearest_transform_size(Int32(n), pffft_transform_t(type), higher ? 1 : 0))
-    }
-
-    deinit {
-        pffftd_destroy_setup(ptr)
-    }
-}
-
-extension Double: FFTElement {
-    public typealias FFTImpl = FFTDouble
-}
diff --git a/Packages/PFFFT/Sources/PFFFT/FFTFloat.swift b/Packages/PFFFT/Sources/PFFFT/FFTFloat.swift
deleted file mode 100644
index 9b0d05a..0000000
--- a/Packages/PFFFT/Sources/PFFFT/FFTFloat.swift
+++ /dev/null
@@ -1,75 +0,0 @@
-internal import PFFFTLib
-
-public final class FFTFloat: PFFFTProtocol {
-    let ptr: OpaquePointer
-    let n: Int
-    let type: FFTType
-
-    static let sharedCache = SetupCache<Element>()
-
-    public static func setup(for n: Int, type: FFTType) throws -> FFTFloat {
-        try sharedCache.get(for: n, type: type)
-    }
-
-    public init(n: Int, type: FFTType) throws {
-        guard let ptr = pffft_new_setup(Int32(n), pffft_transform_t(type)) else { throw FFTError.invalidSize }
-        self.ptr = ptr
-        self.n = n
-        self.type = type
-    }
-
-    public func forward(input: borrowing Buffer<Float>, output: borrowing Buffer<Float>, work: borrowing Buffer<Float>?, sign: FFTSign) {
-        checkFftBufferCounts(n: n, type: type, input: input, output: output, work: work)
-
-        let workAddress: UnsafeMutablePointer<Float>! = switch work {
-        case let .some(b): b.baseAddress
-        case .none: nil
-        }
-        pffft_transform_ordered(ptr, input.baseAddress, output.baseAddress, workAddress, pffft_direction_t(sign))
-    }
-
-    public func fftUnordered(input: borrowing Buffer<Float>, output: borrowing Buffer<Float>, work: borrowing Buffer<Float>?, sign: FFTSign) {
-        checkFftBufferCounts(n: n, type: type, input: input, output: output, work: work)
-
-        let workAddress: UnsafeMutablePointer<Float>! = switch work {
-        case let .some(b): b.baseAddress
-        case .none: nil
-        }
-        pffft_transform(ptr, input.baseAddress, output.baseAddress, workAddress, pffft_direction_t(sign))
-    }
-
-    public func reorderSpectrum(input: borrowing Buffer<Float>, output: borrowing Buffer<Float>) {
-        checkFftBufferCounts(n: n, type: type, input: input, output: output, work: nil)
-        pffft_zreorder(ptr, input.baseAddress, output.baseAddress, PFFFT_FORWARD)
-    }
-
-    public func convolveAccumulate(dftA: borrowing Buffer<Float>, dftB: borrowing Buffer<Float>, dftAB: borrowing Buffer<Float>, scaling: Float) {
-        checkConvolveBufferCounts(n: n, type: type, a: dftA, b: dftB, ab: dftAB)
-        pffft_zconvolve_accumulate(ptr, dftA.baseAddress, dftB.baseAddress, dftAB.baseAddress, scaling)
-    }
-
-    public func convolve(dftA: borrowing Buffer<Float>, dftB: borrowing Buffer<Float>, dftAB: borrowing Buffer<Float>, scaling: Float) {
-        checkConvolveBufferCounts(n: n, type: type, a: dftA, b: dftB, ab: dftAB)
-        pffft_zconvolve_no_accu(ptr, dftA.baseAddress, dftB.baseAddress, dftAB.baseAddress, scaling)
-    }
-
-    public static func minFftSize(for type: FFTType) -> Int {
-        Int(pffft_min_fft_size(pffft_transform_t(type)))
-    }
-
-    public static func isValidSize(_ n: Int, for type: FFTType) -> Bool {
-        pffft_is_valid_size(Int32(n), pffft_transform_t(type)) != 0
-    }
-
-    public static func nearestValidSize(_ n: Int, for type: FFTType, higher: Bool) -> Int {
-        Int(pffft_nearest_transform_size(Int32(n), pffft_transform_t(type), higher ? 1 : 0))
-    }
-
-    deinit {
-        pffft_destroy_setup(ptr)
-    }
-}
-
-extension Float: FFTElement {
-    public typealias FFTImpl = FFTFloat
-}
diff --git a/Packages/PFFFT/Sources/PFFFT/PFFFT.swift b/Packages/PFFFT/Sources/PFFFT/PFFFT.swift
index 007f6d5..f2a5b1d 100644
--- a/Packages/PFFFT/Sources/PFFFT/PFFFT.swift
+++ b/Packages/PFFFT/Sources/PFFFT/PFFFT.swift
@@ -1,27 +1,12 @@
 internal import PFFFTLib
+import ComplexModule
+import RealModule
 
-@frozen
-public enum FFTType {
-    case real
-    case complex
-}
 
-@frozen
-public enum FFTSign: Int {
-    case forward = -1
-    case backward = 1
-}
-
-public enum FFTError: Error {
-    case invalidSize
-}
-
-public protocol FFTElement {
-    associatedtype FFTImpl: PFFFTProtocol
-}
-
-public protocol PFFFTProtocol<Element> {
-    associatedtype Element
+public protocol PFFFTProtocol<T> {
+    associatedtype T: FFTElemental
+    associatedtype ComplexType = T.ComplexType
+    associatedtype ScalarType = T.ScalarType
 
     /// Get an FFT interface for the given size and FFT Type.
     ///
@@ -31,14 +16,14 @@ public protocol PFFFTProtocol<Element> {
     /// - type: The type of FFT.
     /// - Returns: An FFT interface.
     /// - Throws: `FFTError.invalidSize` if the size is invalid.
-    static func setup(for n: Int, type: FFTType) throws -> Self
+    static func setup(for n: Int) throws -> Self
 
     /// Initialize the FFT implementation with the given size and type.
     /// - Parameters:
     /// - n: The size of the FFT.
     /// - type: The type of FFT.
     /// - Throws: `FFTError.invalidSize` if the size is invalid.
-    init(n: Int, type: FFTType) throws
+    init(n: Int) throws
 
     /// Perform a forward FFT on the input buffer.
     ///
@@ -60,9 +45,9 @@ public protocol PFFFTProtocol<Element> {
     ///  - output: The output buffer.
     ///  - work: An optional work buffer. Must have capacity of at least `n` for real FFTs and `2 * n` for complex FFTs.
     ///  - sign: The direction of the FFT.
-    func forward(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?)
+    func forward(input: borrowing Buffer<T>, output: borrowing Buffer<ComplexType>)
 
-    func inverse(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?)
+    func inverse(input: borrowing Buffer<ComplexType>, output: borrowing Buffer<T>)
 
     /// Perform a forward FFT on the input buffer, with implementation defined order.
     ///
@@ -73,22 +58,11 @@ public protocol PFFFTProtocol<Element> {
     ///  - output: The output buffer.
     ///  - work: An optional work buffer. Must have capacity of at least `n` for real FFTs and `2 * n` for complex FFTs.
     ///  - sign: The direction of the FFT.
-    func forwardUnordered(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?)
+    func forwardToInternalLayout(input: borrowing Buffer<T>, output: borrowing Buffer<ScalarType>)
 
-    func inverseUnordered(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?)
+    func inverseFromInternalLayout(input: borrowing Buffer<ScalarType>, output: borrowing Buffer<T>)
 
-    func reorder(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, sign: FFTSign)
-
-    /// Perform a convolution of two complex signals in the frequency domain.
-    ///
-    /// Multiplies frequency domain components of `dftA` and `dftB` and accumulates the result in `dftAB`.
-    /// The operation performed is `dftAB += (dftA * dftB) * scaling`.
-    /// - Parameters:
-    /// - dftA: The first input buffer of frequency domain data.
-    /// - dftB: The second input buffer of frequency domain data.
-    /// - dftAB: The output buffer of frequency domain data.
-    /// - scaling: The scaling factor to apply to the result.
-    func convolveAccumulate(dftA: borrowing Buffer<Element>, dftB: borrowing Buffer<Element>, dftAB: borrowing Buffer<Element>, scaling: Element)
+    func reorder(spectrum: borrowing Buffer<ScalarType>, output: borrowing Buffer<ComplexType>)
 
     /// Perform a convolution of two complex signals in the frequency domain.
     ///
@@ -99,12 +73,24 @@ public protocol PFFFTProtocol<Element> {
     /// - dftB: The second input buffer of frequency domain data.
     /// - dftAB: The output buffer of frequency domain data.
     /// - scaling: The scaling factor to apply to the result.
-    func convolve(dftA: borrowing Buffer<Element>, dftB: borrowing Buffer<Element>, dftAB: borrowing Buffer<Element>, scaling: Element)
+    func convolve(dftA: borrowing Buffer<ScalarType>, dftB: borrowing Buffer<ScalarType>, dftAB: borrowing Buffer<ScalarType>, scaling: ScalarType)
+
+    /// Perform a convolution of two complex signals in the frequency domain.
+    ///
+    /// Multiplies frequency domain components of `dftA` and `dftB` and accumulates the result in `dftAB`.
+    /// The operation performed is `dftAB += (dftA * dftB) * scaling`.
+    /// - Parameters:
+    /// - dftA: The first input buffer of frequency domain data.
+    /// - dftB: The second input buffer of frequency domain data.
+    /// - dftAB: The output buffer of frequency domain data.
+    /// - scaling: The scaling factor to apply to the result.
+    func convolveAccumulate(dftA: borrowing Buffer<ScalarType>, dftB: borrowing Buffer<ScalarType>, dftAB: borrowing Buffer<ScalarType>, scaling: ScalarType)
+
 
     /// Returns the minimum FFT size for the given type.
     ///
     /// - Parameter type: The type of FFT.
-    static func minFftSize(for type: FFTType) -> Int
+    static func minFftSize() -> Int
 
     /// Returns whether the given size is valid for the given type.
     ///
@@ -112,10 +98,10 @@ public protocol PFFFTProtocol<Element> {
     /// - Parameters:
     /// - n: The size to check.
     /// - type: The type of FFT.
-    static func isValidSize(_ n: Int, for type: FFTType) -> Bool
+    static func isValidSize(_ n: Int) -> Bool
 
     /// Returns the nearest valid size for the given type.
-    static func nearestValidSize(_ n: Int, for type: FFTType, higher: Bool) -> Int
+    static func nearestValidSize(_ n: Int, higher: Bool) -> Int
 }
 
 public var simdArch: String {
@@ -142,37 +128,3 @@ extension pffft_direction_t {
     }
 }
 
-@inline(__always)
-func checkFftBufferCounts<Element>(n: Int, type: FFTType, input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?) {
-    let minSize = type == .real ? n : 2 * n
-
-    let work: UnsafeMutableBufferPointer<Element>! = switch work {
-    case let .some(b): b.buffer
-    case .none: nil
-    }
-
-    guard input.count >= minSize else {
-        fatalError("input buffer too small")
-    }
-    guard output.count >= minSize else {
-        fatalError("output buffer too small")
-    }
-    guard work == nil || work.count >= minSize else {
-        fatalError("work buffer too small")
-    }
-}
-
-@inline(__always)
-func checkConvolveBufferCounts<Element>(n: Int, type: FFTType, a: borrowing Buffer<Element>, b: borrowing Buffer<Element>, ab: borrowing Buffer<Element>) {
-    let minSize = type == .real ? n : 2 * n
-
-    guard a.count >= minSize else {
-        fatalError("a buffer too small")
-    }
-    guard b.count >= minSize else {
-        fatalError("b buffer too small")
-    }
-    guard ab.count >= minSize else {
-        fatalError("ab buffer too small")
-    }
-}
diff --git a/Packages/PFFFT/Sources/PFFFT/SetupCache.swift b/Packages/PFFFT/Sources/PFFFT/SetupCache.swift
index 10bbc29..8bb3c73 100644
--- a/Packages/PFFFT/Sources/PFFFT/SetupCache.swift
+++ b/Packages/PFFFT/Sources/PFFFT/SetupCache.swift
@@ -1,28 +1,24 @@
 import Foundation
 
-struct CacheKey : Hashable {
-    let n: Int
-    let type: FFTType
-}
-
-public class SetupCache<Element: FFTElement> : @unchecked Sendable {
-    private var cache: [CacheKey: Element.FFTImpl?] = [:]
+public class SetupCache<T: FFTElemental> : @unchecked Sendable {
+    typealias FFTType = FFT<T>
+    private var cache: [Int: FFT<T>] = [:]
 
     private let queue = DispatchQueue(label: String(describing: SetupCache.self), attributes: .concurrent)
 
     public init() {}
 
-    public func get(for n: Int, type: FFTType) throws -> Element.FFTImpl {
-        var setup: Element.FFTImpl??
+    public func get(for n: Int) throws -> FFT<T> {
+        var setup: FFTType??
         queue.sync {
-            setup = cache[CacheKey(n: n, type: type)]
+            setup = cache[n]
         }
         if setup == nil {
             queue.sync(flags: .barrier) {
-                setup = cache[CacheKey(n: n, type: type)]
+                setup = cache[n]
                 if setup == nil {
-                    let entry = try? Element.FFTImpl(n: n, type: type)
-                    cache[CacheKey(n: n, type: type)] = entry
+                    let entry = try? FFTType(n: n)
+                    cache[n] = entry
                     setup = entry
                 }
             }
diff --git a/Sources/EcgSynKit/EcgSynKit.swift b/Sources/EcgSynKit/EcgSynKit.swift
index 96e2860..a7cad99 100644
--- a/Sources/EcgSynKit/EcgSynKit.swift
+++ b/Sources/EcgSynKit/EcgSynKit.swift
@@ -1,7 +1,9 @@
 import Algorithms
+import ComplexModule
 import Foundation
-import PFFFTLib
 import PFFFT
+import PFFFTLib
+import RealModule
 
 struct Parameters {
     /// The number of beats to simulate.
@@ -63,75 +65,70 @@ func stdev(_ data: [Double]) -> Double {
     return sqrt(data.lazy.map { ($0 - mean) * ($0 - mean) }.reduce(0.0, +) / (n - 1))
 }
 
-struct RRProcess : ~Copyable {
+struct RRProcess: ~Copyable {
     let nrr: Int
 
-    let input: Buffer<Double>
-    let output: Buffer<Double>
-    let work: Buffer<Double>
-    let fft: FFTDouble
+    let spectrum: Buffer<Complex<Double>>
+    let signal: Buffer<Double>
+    let fft: FFT<Double>
 
     init(nrr: Int) {
         self.nrr = nrr
-        self.input = Buffer<Double>(capacity: nrr + 2)
-        self.output = Buffer<Double>(capacity: nrr)
-        self.work = Buffer<Double>(capacity: nrr)
-        self.fft = try! FFTDouble.setup(for: nrr, type: .real)
+        fft = try! FFT<Double>(n: nrr)
+        spectrum = fft.makeSpectrumBuffer()
+        signal = fft.makeSignalBuffer()
     }
 
     func generate(params: Parameters) -> [Double] {
+        let w1 = 2.0 * .pi * params.flo
+        let w2 = 2.0 * .pi * params.fhi
+        let c1 = 2.0 * .pi * params.flostd
+        let c2 = 2.0 * .pi * params.fhistd
 
-            let w1 = 2.0 * .pi * params.flo
-    let w2 = 2.0 * .pi * params.fhi
-    let c1 = 2.0 * .pi * params.flostd
-    let c2 = 2.0 * .pi * params.fhistd
+        let sig2 = 1.0
+        let sig1 = params.lfhfRatio
 
-    let sig2 = 1.0
-    let sig1 = params.lfhfRatio
+        let rrmean = 60.0 / params.hrMean
+        let rrstd = 60.0 * params.hrStd / (params.hrMean * params.hrMean)
 
-    let rrmean = 60.0 / params.hrMean
-    let rrstd = 60.0 * params.hrStd / (params.hrMean * params.hrMean)
+        let sf = Double(params.sfInternal)
+        let df = sf / Double(nrr)
 
-    let sf = Double(params.sfInternal)
-    let df = sf / Double(nrr)
+        spectrum.withUnsafeMutableBufferPointer { swc in
+            for i in 0 ..< nrr / 2 + 1 {
+                let w = df * Double(i) * 2.0 * .pi
+                let dw1 = w - w1
+                let dw2 = w - w2
+                let hw = sig1 * exp(-dw1 * dw1 / (2.0 * c1 * c1)) / sqrt(2.0 * .pi * c1 * c1)
+                    + sig2 * exp(-dw2 * dw2 / (2.0 * c2 * c2)) / sqrt(2.0 * .pi * c2 * c2)
 
-    input.withUnsafeMutableBufferPointer { swc in
-        for i in 0 ..< nrr / 2 + 1 {
-            let w = df * Double(i) * 2.0 * .pi
-            let dw1 = w - w1
-            let dw2 = w - w2
-            let hw = sig1 * exp(-dw1 * dw1 / (2.0 * c1 * c1)) / sqrt(2.0 * .pi * c1 * c1)
-                + sig2 * exp(-dw2 * dw2 / (2.0 * c2 * c2)) / sqrt(2.0 * .pi * c2 * c2)
+                let sw = (sf / 2.0) * sqrt(hw)
+                let ph = 2.0 * .pi * Double.random(in: 0.0 ..< 1.0)
 
-            let sw = (sf / 2.0) * sqrt(hw)
-            let ph = 2.0 * .pi * Double.random(in: 0.0 ..< 1.0)
+                swc[i].real = sw * cos(ph)
+                swc[i].imaginary = sw * sin(ph)
+            }
 
-            swc[i * 2] = sw * cos(ph)
-            swc[i * 2 + 1] = sw * sin(ph)
+            // pack Nyquist frequency real to imaginary of DC
+            swc[0].imaginary = swc[nrr / 2].real
         }
 
-        // pack Nyquist frequency real to imaginary of DC
-        swc[1] = swc[nrr]
-    }
+        fft.inverse(spectrum: spectrum, signal: signal)
 
-    self.fft.forward(input: input, output: output, work: nil, sign: .backward)
+        var rr = signal.withUnsafeMutableBufferPointer { outptr in
+            outptr.map { $0 * 1.0 / Double(nrr) }
+        }
 
-    var rr = output.withUnsafeMutableBufferPointer { outptr in
-        return outptr.map { $0 * 1.0 / Double(nrr) }
-    }
-
-    let xstd = stdev(rr)
-    let ratio = rrstd / xstd
-
-    for i in 0 ..< nrr {
-        rr[i] = rr[i] * ratio + rrmean
-    }
-    return rr
+        let xstd = stdev(rr)
+        let ratio = rrstd / xstd
 
+        for i in 0 ..< nrr {
+            rr[i] = rr[i] * ratio + rrmean
+        }
+        return rr
     }
 }
 
-
 // func compute(params: Parameters) {
 //     // adjust extrema parameters for mean heart rate
 //     let hrFact = sqrt(params.hrMean / 60)
diff --git a/Tests/EcgSynKitTests/EcgSynKitTests.swift b/Tests/EcgSynKitTests/EcgSynKitTests.swift
index e18059b..2df535f 100644
--- a/Tests/EcgSynKitTests/EcgSynKitTests.swift
+++ b/Tests/EcgSynKitTests/EcgSynKitTests.swift
@@ -6,7 +6,8 @@ import Testing
     let p = Parameters()
 
 
-    let rr = rrprocess(params: p, nrr: 131072)
+    let rrp = RRProcess(nrr: 131072)
+    let rr = rrp.generate(params: p)
     //fft(data: &a, isign: -1)
     //print("out: \(rr)")