tur-signal

Arrow-based signal processing for Turmeric: Signal Function (SF) combinators, DSP filters, ADSR envelopes, and synthesizer voices.

Overview

tur-signal provides a composable signal processing pipeline built on Turmeric's Arrow typeclass:

signal/core -- Signal type, SF arrow combinators (constant, time-signal, sample, map-signal, pair-signals)
signal/dsp -- Oscillators (sine, square, sawtooth), filters (low-pass, high-pass), amplitude ops (gain, mix, add)
signal/envelope -- Piecewise-linear ADSR envelope generator (adsr-fixed, ADSRParams)
signal/synth -- Synthesizer voices and effects (voice, fm-voice, wavetable-osc, karplus-strong, presets, effects-chain, step-sequencer)

Installation

Add tur-signal to your build.tur :spices block:

(defpackage my-app
  :spices #{
    "signal" #{:url    "https://github.com/rjungemann/turmeric-spices"
               :ref    "signal-v0.1.0"
               :subdir "spices/signal"}
  })

Then fetch:

tur fetch

Quick Start

(import signal/core)
(import signal/dsp)
(import signal/envelope)

;; 440 Hz sine wave sampled at t=0.0
(let [sine-sf (sine 440.0 0.0)
      dummy   (constant ())
      out     (sine-sf dummy)]
  (println (out 0.0)))    ; => ~0.0

;; Chained: sine -> low-pass filter
(let [osc     (sine 440.0 0.0)
      filt    (low-pass 0.3)
      sig     ((osc (constant ())))
      filtered (filt sig)]
  (println (filtered 0.001)))

;; ADSR envelope
(let [params (ADSRParams 0.01 0.1 0.7 0.3)
      env    (adsr-fixed params 0.5)
      out    (env (constant ()))]
  (println (out 0.005)))  ; => ~0.5 (mid-attack)

Module Reference

`signal/core`

Symbol	Description
`constant val`	Signal that always returns `val`
`time-signal t`	Signal that returns `t` at each sample
`sample sig t`	Evaluate signal `sig` at time `t`
`map-signal f sig`	Lift pure function `f` over signal pointwise
`pair-signals sig-a sig-b`	Zip two signals into a Pair signal
`left-signal sig`	Identity injection (Left branch placeholder)
`right-signal sig`	Identity injection (Right branch placeholder)

`signal/dsp`

Symbol	Description
`sine freq phase`	Sine-wave SF at `freq` Hz with phase offset
`square freq duty`	Square-wave SF with duty cycle
`sawtooth freq`	Sawtooth-wave SF
`low-pass alpha`	First-order IIR low-pass filter SF
`high-pass alpha`	First-order IIR high-pass filter SF
`gain g`	Scale signal by constant factor `g`
`mix alpha`	Weighted mix of a Pair signal
`add`	Sample-wise sum of a Pair signal

`signal/envelope`

Symbol	Description
`ADSRParams attack decay sustain release`	ADSR parameter struct
`adsr-fixed params gate-duration`	Piecewise-linear ADSR envelope SF

`signal/synth`

Synthesizer voices, wavetable oscillators, granular synthesis, FM, Karplus-Strong string model, effects chain, and step sequencer. See source for full API.

Examples

Examples live in examples/:

cd ../turmeric-spices/spices/signal
tur run examples/01_basics.tur
tur run examples/02_signals.tur
tur run examples/03_dsp.tur

Development

cd spices/signal
tur check src/signal/synth.tur   # typecheck
tur run tests/signal/arrow_tests.tur  # run tests

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