FYampaSynth 1.0.0

Modular Synthesizer Programming in F#

Overview

FYampaSynth is a modular music synthesizer in F# that's inspired by Haskell's Yampa and YampaSynth. It is based on the concept of a "signal function", which maps an input signal to an output signal:

type SignalFunction<'a, 'b> = Signal<'a> -> Signal<'b>

Where a "signal" is (conceptually) a function from time to values of some type:

type Signal<'a> = Time -> 'a

Signal functions are first-class objects in Yampa, and can be composed using "arrow" combinators to synthesize music in software.

FYampaSynth uses NAudio to generate sound, and hence is Windows-only.

Examples

A simple sine wave can be generated as follows:

open FYampaSynth
open Arrow

use engine = new AudioEngine()
Synth.oscSine 440.0   // A above middle C
    >>^ (*) 0.05      // reduce volume (sine waves are obnoxious!)
    |> Synth
    |> engine.AddInput

To make a slightly more interesting synthesizer, we can use a sawtooth wave instead and slowly oscillate its frequency:

Synth.oscSine 1.0   // low-frequency control value
    >>> Synth.oscSawtooth 440.0

More pleasingly, we can emulate an old Moog synthesizer (via subtractive synthesis), like this:

(Synth.oscSawtooth 440.00
    &&& Synth.oscSine 1.0)        // note and oscillation
    >>> Synth.moogVcf 880.0 0.5   // filter frequencies above 880 hz

Additional references

• Modular Synthesizer Programming in Haskell: Paper describing the original YampaSynth.
• The Yampa Implementation: Practical guide to implementing Yampa.
• Fire and Forget Audio Playback with NAudio