MoogSynth

This is an example of a real-time Unity synthesizer with a Moog filter simulation.

It has a monophonic pulse-width modulated square wave and a saw wave (using polyBLEP for band-limiting), with a sub sine wave (one octave lower), and a resonant Moog-simulation filter based on the Huovilainen model. The filter frequency is controlled by a simple ramp envelope, and the amplitude is controlled by an ADSR envelope.

The synthesizer is controlled using a thread safe event queue, and note events can be sent from normal Unity MonoBehaviours. Note events can be note on and off, have a pitch, and a time stamp, which is measured in samples.

Sequencer.cs is a step sequencer component that demonstrates how to implement sequencing and how to convert BPM to sample ticks.

Sample-accurate Sequencing

Here is an example of how to compute time stamps corresponding to a given tempo (in BPM):

MoogSynth synth;
const Int64 bufferTime = 2048; // experiment to find the lowest value that works on everything (in samples)
float tempo_bpm = 120;
Int64 tempo_smpPerNote;
Int64 nextNoteTime; // (in samples)

void Start()
{
    tempo_smpPerNote = (Int64)(60 * AudioSettings.outputSampleRate / tempo_bpm);

    // First note is played at a reasonable point in the near future
    nextNoteTime = synth.GetTime_smp() + buffertime; // as soon as possible
}

void Update()
{
    Int64 time = synth.GetTime_smp();

    // Time to queue a new note?
    while(time + bufferTime >= nextNoteTime)
    {
        int pitch = UnityEngine.Random.Range(30,90);
        synth.queue_event(EventQueue.EventType.Note_on, pitch, nextNoteTime);

        // From here on, all notes are sample accurate in relation to the first note
        noteOnTime += tempo_smpPerNote;
    }
}