PatchCore is an open-source Kotlin Multiplatform library for building modular synthesizers and audio processing applications.
At its core, PatchCore is written in portable C++, enabling high-performance audio processing across platforms—from mobile and desktop to embedded systems. The Kotlin interface provides a modern, idiomatic API for composing and connecting audio modules in a flexible patching environment.
PatchCore is designed to let you build performant and agile synthesizers entirely in Kotlin, without needing to dive into C++ internals. At the same time, it offers deep flexibility: you can implement custom modules in C++ and expose them to Kotlin with just a few lightweight, template-based wrappers — or, in simple cases, with no additional code at all.
class SoundEngine {
class Synth: ModularSynth() {
// PolyModule(name, polyphonyCount = 8)
class Voice(name: String): PatchModule(name) {
val keyboard by module( KeyboardModule("keyboard") )
val vco by module( VcoModule("vco") ) {
userWaveForm.setValue(WaveForm.SQUARE)
userPwm.setValue(0.5f)
}
val env by module(ADSREnvelopeModule("env") )
val vca by module(VcaModule("vca"))
val vcf by module( BiQuadVCFModule("vcf"))
val lfo by module( LfoModule("lfo") )
val pitchLfoAmount by module( AttenuverterModule("pitchAmount") )
val cutoffLfoAmount by module( AttenuverterModule("cutoffAmount") )
val cutoffEnvAmount by module( AttenuverterModule("cutoffEnvAmount") )
val output = createOutput(vcf.output)
override val defaultPatch = createPatch {
keyboard.cv patchTo vco.cv
vco.output patchTo vca.input
keyboard.gate patchTo env.gate
env.output patchTo vcf.input
lfo.output patchTo pitchLfoAmount.input
pitchLfoAmount.output patchTo vco.cv
lfo.output patchTo cutoffLfoAmount.input
cutoffLfoAmount.output patchTo vcf.cutoff
env.output patchTo cutoffEnvAmount.input
cutoffEnvAmount.output patchTo vcf.cutoff
}
}
val voice by module( Voice("voice") )
override val defaultPatch = createPatch {
voice.output patchTo monoOutput
}
}
private val patchCore = PatchCore()
private val synth = patchCore.createSynth(Synth())
private val audioInterface: AudioInterface = patchCore.createAudioInterface().apply {
setOptions( AndroidAudioInterfaceOptions(), /*..., iOSAudioInterfaceOptions*/ )
setSynth(synth)
}
// should be tied to the lifecycle of the app
fun start() {
audioInterface.start()
}
// should be tied to the lifecycle of the app
fun stop() {
audioInterface.stop()
}
// keyboard events
fun onKeyDown(note: Float) {
synth.voice.keyboard.onPress(note)
}
fun onKeyUp(note: Float) {
synth.voice.keyboard.onRelease(note)
}
// set parameters values of the synth
fun setCutoffValue(cutoff: Float) {
synth.voice.vcf.userCutoff.setValue(cutoff)
}
//...
}Add the dependency to your build.gradle.kts
// for kotlin multiplatform projects
commonMain.dependencies {
implementation("com.sillydevices.patchcore:patchcore-multiplatform:0.2.6")
}
// for android projects
dependencies {
implementation("com.sillydevices.patchcore:patchcore-multiplatform:0.2.6")
// or
implementation("com.sillydevices.patchcore:patchcore-multiplatform-android:0.2.6")
}
Don’t forget to add a swift package dependency to your iOS project from https://github.com/SillyDevices/PatchCore
patchcore-multiplatform-android is supplied as an AAR artifact with unstripped native libraries. Make sure to strip them in release builds to reduce the size of your app.
By default AGP strip native libraries only if you have ndk installed. Ensure you have it installed on your LOCAL and CI machines. AGP just skips stripReleaseDebugSymbols if ndk is not found.
## Using for development as submodule
Initialize the Git submodule and add it to your project
```bash
git submodule init
git submodule add git@github.com:SillyDevices/PatchCore.git PatchCore
git submodule update --init --recursive PatchCore
cp local.properties PatchCore/local.propertiesThen, include the submodule in your build setup: settings.gradle.kts
includeBuild("PatchCore") {
dependencySubstitution {
substitute(module("com.sillydevices.patchcore:native-android")).using(project(":PatchCore"))
substitute(module("com.sillydevices.patchcore:patchcore-multiplatform")).using(project(":PatchCoreMultiplatform"))
substitute(module("com.sillydevices.patchcore:patchcore-multiplatform-android")).using(project(":PatchCoreMultiplatform"))
}
}add dependency to app module build.gradle.kts
//build.gradle.kts
dependencies {
implementation("com.sillydevices.patchcore:patchcore-multiplatform:0.2.6")
}add local swift package dependency to your iOS project from PatchCore folder