SonixLessonSynthesizer

Synthesize audio lessons from note sequences (e.g. Sa Re Ga in Indian classical practice), each with its own audio recording.

Quick Start

Kotlin

val notes = listOf(
    LessonNote(
        noteName = "Sa",
        noteLabel = "S",
        noteAudioFilePath = "/path/to/sa.wav",
        numBeats = 2,
        numSamplesConsonant = 100
    ),
    LessonNote(
        noteName = "Re",
        noteLabel = "R",
        noteAudioFilePath = "/path/to/re.wav",
        numBeats = 2,
        numSamplesConsonant = 100
    )
)

val synth = SonixLessonSynthesizer.create(
    notes = notes,
    beatLengthMs = 500
)

if (synth.loadAudioSync()) {
    val audioData: AudioRawData? = synth.synthesize()
    // audioData is ready to play or save
}

synth.release()

Swift

let notes = [
    LessonNote(
        noteName: "Sa",
        noteLabel: "S",
        noteAudioFilePath: "/path/to/sa.wav",
        numBeats: 2,
        numSamplesConsonant: 100
    ),
    LessonNote(
        noteName: "Re",
        noteLabel: "R",
        noteAudioFilePath: "/path/to/re.wav",
        numBeats: 2,
        numSamplesConsonant: 100
    )
]

let synth = SonixLessonSynthesizer.create(
    notes: notes,
    beatLengthMs: 500
)

if await synth.loadAudio() {
    if let audioData = synth.synthesize() {
        // audioData is ready to play or save
    }
}

synth.release()

Configuration

Factory Method

Parameter	Type	Default	Description
notes	List<LessonNote>	—	Note sequence (required)
beatLengthMs	Int	—	Beat duration in milliseconds (required)

Builder

For advanced configuration:

Kotlin

val synth = SonixLessonSynthesizer.Builder()
    .notes(noteList)
    .beatLengthMs(500)
    .silenceBeats(start = 2, end = 2)
    .sampleRate(44100)
    .onError { error -> println("Error: $error") }
    .build()

Builder Parameters

Method	Type	Default	Description
notes	List<LessonNote>	—	Note sequence (required)
beatLengthMs	Int	—	Beat duration in ms (required)
silenceBeats	start: Int, end: Int	2, 2	Silence beats at start/end
sampleRate	Int	16000	Output sample rate in Hz
onError	(String) -> Unit	—	Error callback

Workflow

The synthesis process has two steps:

1. Load Audio

Load note audio files into memory:

// Suspending (preferred)
val success = synth.loadAudio()

// Synchronous (blocking)
val success = synth.loadAudioSync()

2. Synthesize

Generate the lesson track:

val audioData: AudioRawData? = synth.synthesize()
if (audioData != null) {
    // Play it
    val player = SonixPlayer.createFromPcm(
        data = audioData.audioData,
        sampleRate = audioData.sampleRate,
        channels = audioData.numChannels
    )
    player.play()
}

Observing State

Kotlin (StateFlow)

synth.isLoading.collect { loading ->
    progressBar.isVisible = loading
}

synth.isLoaded.collect { loaded ->
    synthesizeButton.isEnabled = loaded
}

synth.error.collect { error ->
    error?.let { showError(it.message) }
}

Swift (Observers)

let loadingTask = synth.observeIsLoading { loading in
    self.isLoading = loading
}

let loadedTask = synth.observeIsLoaded { loaded in
    self.isReady = loaded
}

let errorTask = synth.observeError { error in
    if let error = error { self.showError(error.message) }
}

Swift (Combine)

synth.isLoadingPublisher
    .receive(on: DispatchQueue.main)
    .sink { self.isLoading = $0 }
    .store(in: &cancellables)

StateFlows

StateFlow	Type	Description
isLoading	StateFlow<Boolean>	Whether audio files are being loaded
isLoaded	StateFlow<Boolean>	Whether ready for synthesis
error	StateFlow<SonixError?>	Error state

Properties

Property	Type	Description
beatLengthMs	Int	Beat duration in milliseconds
silenceBeatsStart	Int	Silence beats at the start
silenceBeatsEnd	Int	Silence beats at the end
sampleRate	Int	Output sample rate

LessonNote

Each note in the sequence is defined by:

Property	Type	Description
noteName	String	Full name (e.g., "Sa", "Re")
noteLabel	String	Short label (e.g., "S", "R")
noteAudioFilePath	String	Path to audio recording
numBeats	Int	Duration in beats
numSamplesConsonant	Int	Consonant samples for crossfading

Method Summary

Method	Returns	Description
loadAudio()	Boolean	Load audio files (suspend / async)
loadAudioSync()	Boolean	Load audio files (blocking)
synthesize()	AudioRawData?	Generate lesson audio
release()	—	Release resources

Next Steps

• SonixMidiSynthesizer — MIDI-based synthesis
• SonixPlayer — Play synthesized audio
• SonixEncoder — Save synthesized audio to file