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DaisySP DSP Module Catalog & API Reference

This reference document provides an exhaustive, parameter-by-parameter catalog of all 60+ DSP modules across both the MIT Core and LGPL Submodule of the DaisySP library.

1. Synthesis Modules

Oscillator (MIT)

  • Header: Synthesis/oscillator.h
  • Waveforms: WAVE_SIN, WAVE_TRI, WAVE_SAW, WAVE_RAMP, WAVE_SQUARE, WAVE_POLYBLEP_TRI, WAVE_POLYBLEP_SAW, WAVE_POLYBLEP_SQUARE
  • API:
  • void Init(float sample_rate): Sets defaults (100 Hz, amp 0.5, sine).
  • void SetWaveform(uint8_t wf): Selects waveform enum.
  • void SetFreq(float freq): Sets fundamental frequency in Hz.
  • void SetAmp(float amp): Sets amplitude (\(0.0 - 1.0\)).
  • void SetPw(float pw): Sets pulse width for square waveforms (\(0.0 - 1.0\)).
  • bool IsEOR(): True if cycle is at end-of-rise.
  • float Process(): Computes next audio sample.

Fm2 (MIT)

  • Header: Synthesis/fm2.h
  • Architecture: 2-operator Phase Modulation (FM).
  • API:
  • void Init(float sample_rate): Initializes carrier and modulator.
  • void SetFrequency(float freq): Carrier frequency in Hz.
  • void SetRatio(float ratio): Ratio of modulator to carrier.
  • void SetIndex(float index): Modulation depth / index.
  • float Process(): Evaluates FM output sample.

VariableShapeOscillator (MIT)

  • Header: Synthesis/variableshapeosc.h
  • Origin: Ported from Mutable Instruments Plaits (variable_shape_oscillator.h).
  • API:
  • void Init(float sample_rate)
  • void SetFreq(float freq)
  • void SetWaveshape(float shape): \(0.0\) = saw/ramp/triangle, \(1.0\) = square.
  • void SetPW(float pw): Controls symmetry/pulse width.
  • void SetSync(bool sync): Enables internal hard sync oscillator.
  • float Process()

VariableSawOscillator (MIT)

  • Header: Synthesis/variablesawosc.h
  • Origin: Mutable Instruments Plaits. Morphs between variable ramp slopes and notches.
  • API: Init(sr), SetFreq(f), SetPW(pw), SetWaveshape(shape), Process().

FormantOscillator (MIT)

  • Header: Synthesis/formantosc.h
  • Origin: Mutable Instruments Plaits. Dual-formant vocal tract synthesizer.
  • API: Init(sr), SetCarrierFreq(f), SetFormantFreq(f), SetPhaseShift(phase), Process().

HarmonicOscillator (MIT)

  • Header: Synthesis/harmonic_osc.h
  • Architecture: Additive synthesis generating harmonic partials with arbitrary weights.
  • API: Init(sr), SetFreq(f), SetAmplitudes(const float* amps), Process().

OscillatorBank (MIT)

  • Header: Synthesis/oscillatorbank.h
  • Architecture: Parallel detuned oscillator cluster for supersaw and swarm textures.
  • API: Init(sr), SetFreq(f), SetAmplitudes(amps), SetGain(gain), Process().

VosimOscillator (MIT)

  • Header: Synthesis/vosim.h
  • Architecture: Voice simulation decaying sin-squared pulse trains.
  • API: Init(sr), SetFreq(f), SetFormantFreq(f1, f2), SetShape(shape), Process().

ZOscillator (MIT)

  • Header: Synthesis/zoscillator.h
  • Origin: Inspired by Casio CZ phase-distortion and Mutable Instruments Plaits.
  • API: Init(sr), SetFreq(f), SetFormantFreq(f), SetShape(s), SetMode(m), Process().

BlOsc (LGPL)

  • Header: DaisySP-LGPL/Source/Synthesis/blosc.h
  • Origin: Soundpipe / Faust (Julius Smith).
  • Waveforms: WAVE_TRIANGLE, WAVE_SAW, WAVE_SQUARE, WAVE_OFF.
  • API: Init(sr), SetFreq(f), SetAmp(a), SetPw(pw), Process().

2. Filter Modules

Svf (MIT)

  • Header: Filters/svf.h
  • Architecture: Double-sampled stable Chamberlin state-variable filter.
  • Outputs: Simultaneous Lowpass, Highpass, Bandpass, Notch, and Peak.
  • API:
  • void Init(float sample_rate)
  • void SetFreq(float freq): Cutoff frequency in Hz (\(0\) to \(f_s/3\)).
  • void SetRes(float res): Resonance (\(0.0 - 1.0\)).
  • void SetDrive(float drive): Non-linear saturation factor.
  • void Process(float in): Evaluates filter states (returns void).
  • float Low(): Extracts lowpass output.
  • float High(): Extracts highpass output.
  • float Band(): Extracts bandpass output.
  • float Notch(): Extracts notch output.
  • float Peak(): Extracts peak output.

LadderFilter (MIT)

  • Header: Filters/ladder.h
  • Architecture: Huovilainen New Moog (HNM) 4-pole transistor ladder with 4x oversampling.
  • Modes: FilterMode::LP24, LP12, BP24, BP12, HP24, HP12.
  • API:
  • void Init(float sample_rate)
  • void SetFilterMode(FilterMode mode)
  • void SetFreq(float freq): Cutoff in Hz (\(5\text{ Hz}\) to Nyquist).
  • void SetRes(float res): Resonance (\(0.0 - 1.8\), self-oscillates).
  • void SetPassbandGain(float pbg): Mitigates bass drop at high resonance (\(0.0 - 0.5\)).
  • void SetInputDrive(float drv): Drive into tanh clipper (\(0.0 - 4.0\)).
  • float Process(float in): Single sample processing.
  • void ProcessBlock(float* buf, size_t size): In-place block processing.

FIR (MIT)

  • Header: Filters/fir.h
  • Architecture: Template FIR<size_t max_size, size_t max_block>. Automatically activates FIRFilterImplARM (CMSIS-DSP SIMD) on ARM targets with -DUSE_ARM_DSP.
  • API: Init(const float* ir, size_t len, bool reverse), Process(float in), ProcessBlock(src, dst, size).

OnePole (MIT)

  • Header: Filters/onepole.h
  • API: Init(), SetFrequency(f), SetMode(FILTER_MODE_LOW_PASS / HIGH_PASS), Process(in).

Soap (MIT)

  • Header: Filters/soap.h
  • Architecture: Tom Erbe's Second Order All Pass filter.
  • API: Init(sr), SetCenterFreq(f), SetFilterBandwidth(bw), Process(in), Bandpass(), Bandreject().

LGPL Filters

  • MoogLadder: Csound Moog ladder model (Init, SetFreq, SetRes, Process).
  • Biquad: Direct Form I/II biquad IIR filter (Init, SetCutoff, SetRes, Process).
  • Tone / ATone: Csound 1-pole Lowpass and Highpass filters.
  • Comb / Allpass: Feedback delay filters with user buffers.
  • Mode: 2nd-order resonant modal filter.
  • NlFilt: Nonlinear strange attractor feedback filter.

3. Effects Processors

Chorus (MIT)

  • Header: Effects/chorus.h
  • Architecture: Stereo delay modulation network.
  • API: Init(sr), SetLfoFreq(f), SetLfoDepth(d), SetDelayMs(ms), SetPan(l, r), Process(in), GetLeft(), GetRight().

Flanger (MIT)

  • Header: Effects/flanger.h
  • API: Init(sr), SetLfoFreq(f), SetLfoDepth(d), SetFeedback(fb), Process(in).

Phaser (MIT)

  • Header: Effects/phaser.h
  • API: Init(sr), SetLfoFreq(f), SetLfoDepth(d), SetFeedback(fb), SetPoles(p), Process(in).

PitchShifter (MIT)

  • Header: Effects/pitchshifter.h
  • Memory Notice: Allocates internal 16K float delay lines (~128 KB). Place in global memory or SDRAM.
  • API: Init(sr), SetTransposition(semitones), SetDelSize(samples), SetFun(slew), Process(in).

Overdrive (MIT)

Wavefolder (MIT)

Decimator (MIT)

  • Header: Effects/decimator.h
  • API: Init(), SetBitcrushFactor(factor), SetDownsampleFactor(factor), SetBitsToCrush(bits), Process(in).

SampleRateReducer (MIT)

Tremolo (MIT)

  • Header: Effects/tremolo.h
  • API: Init(sr), SetFreq(f), SetDepth(d), SetWaveform(wf), Process(in).

Autowah (MIT)

  • Header: Effects/autowah.h
  • API: Init(sr), SetWah(wah), SetDryWet(dw), SetLevel(lvl), Process(in).

ReverbSc (LGPL)

  • Header: DaisySP-LGPL/Source/Effects/reverbsc.h
  • Memory Notice: Allocates 98,936 floats (~395 KB). Must be placed in SDRAM via DSY_SDRAM_BSS.
  • API:
  • int Init(float sample_rate)
  • void SetFeedback(float fb): Reverb tail length (\(0.0 - 1.0\), \(1.0\) is infinite).
  • void SetLpFreq(float freq): Lowpass damping cutoff in Hz.
  • int Process(const float &in1, const float &in2, float *out1, float *out2)

4. Drum & Percussion Synthesis

AnalogBassDrum (MIT)

  • Header: Drums/analogbassdrum.h
  • API: Init(sr), SetFreq(f), SetTone(t), SetDecay(d), SetAttackFmAmount(a), SetSelfFmAmount(s), SetSustain(bool), SetAccent(a), Trig(), Process(trigger_bool).
  • Output Level & Frequency Caveats:
  • Low Output Amplitude: The raw output of AnalogBassDrum peaks at only \(\approx 0.30\) during its initial 1 ms click transient, and its resonant sine body quickly drops to \(\approx 0.034\) (RMS \(\approx 0.032\), roughly \(-20\text{ dBFS}\) relative to snare/tom models). It requires substantial make-up gain (\(+15\) to \(+20\text{ dB}\)) when mixed with other drum voices.
  • Small Speaker / Audibility Hazard: The bridged-T resonator produces a near-pure sine wave with virtually no upper harmonics. At typical kick fundamentals (\(40 - 60\text{ Hz}\)), it is practically inaudible on miniature built-in hardware speakers (whose acoustic roll-off is \(>150\text{ Hz}\)).
  • SVF Runaway Resonance: SVF resonance is calculated as \(\text{res} = 0.4 \times q \times f\). Above \(\approx 90\text{ Hz}\) or with high decay values, \(\text{res}\) saturates at \(1.0\) (damping drops to \(0.0\)), causing perpetual undamped oscillation that starves control ISRs.
  • Usage Guideline: For punchy, modern kicks that project on built-in speakers and headphones, prefer SyntheticBassDrum or add cubic saturation/drive and beater noise.

SyntheticBassDrum (MIT)

  • Header: Drums/synthbassdrum.h
  • API: Init(sr), SetFreq(f), SetTone(t), SetDecay(d), SetDirtiness(dirt), SetFmEnvelopeAmount(fm), SetFmEnvelopeDecay(fmd), SetAccent(a), Trig(), Process(trigger_bool).
  • Acoustic Characteristics & Advantages:
  • High Output Energy: Modeled after a 909-style kick drum (distorted sine, transistor VCA, pitch FM envelope, click, and attack noise). Evaluates at \(\approx 0.90\) peak and \(\approx 0.38\) RMS (\(+21\text{ dB}\) higher RMS energy than AnalogBassDrum), naturally balancing alongside snares and cymbals.
  • Harmonic Presence for Small Speakers: The SetDirtiness(dirt) parameter controls a distorted sine shaper that injects rich odd harmonics into the body. These mid-frequency harmonics (\(100 - 300\text{ Hz}\)) remain clearly audible even on tiny onboard speakers.
  • Stable Oscillator: Does not use the fragile SVF bridged-T resonator; completely immune to runaway self-oscillation across any tuning range (\(40 - 200\text{ Hz}\)).

AnalogSnareDrum (MIT)

  • Header: Drums/analogsnaredrum.h
  • API: Init(sr), SetFreq(f), SetTone(t), SetDecay(d), SetSnappy(s), SetAccent(a), Trig(), Process(trigger_bool).
  • Critical DSP & Performance Hazards:
  • Undamped SVF Resonance: The resonance for each of the 5 modal resonators is scaled via \(\text{res} = 0.2 \times f \times q\). For typical tuning (\(120 - 400\text{ Hz}\)) and decay values, the calculated resonance argument exceeds \(1.0\) (often \(3.7 - 10.5\)). Inside Svf::SetRes(), this clamps to \(1.0\), which drives damping to zero (\(\text{damp} = 2.0 \times (1.0 - \text{res}^{0.25}) = 0.0\)). Consequently, all 5 resonators enter perpetual undamped self-oscillation, ringing continuously at \(\approx 0.035\) amplitude and preventing voice activity gates from sleeping.
  • Severe Per-Sample CPU Load: In AnalogSnareDrum::Process(), filter coefficients, resonance, and envelope scalings are evaluated inside the per-sample loop rather than at control rate. Each sample computes 14 powf() and 6 sinf() calls across 6 SVF filter instances. On ARM Cortex-M7 (STM32H750 @ 480 MHz), this single module consumes \(\mathbf{65\% - 75\%}\) of the entire 1.0 ms audio block budget.
  • Polyphonic / Overlap DMA Underflow: When overlapped with any other voice (e.g. kick, clap, or hats), aggregate CPU load easily exceeds \(100\%\), causing hardware audio DMA buffer underruns and producing harsh digital static/clicks.
  • Usage Guideline: Avoid AnalogSnareDrum in polyphonic synthesizers or drum machines where multiple voices sound simultaneously. Replace with SyntheticSnareDrum or a custom dual-mode sine oscillator + bandpass noise voice where decay and filter parameters are computed at block rate.

HiHat (MIT)

  • Header: Drums/hihat.h
  • API: Init(sr), SetFreq(f), SetTone(t), SetDecay(d), SetNoisiness(n), SetAccent(a), SetSustain(bool), Process(trigger_bool).

SyntheticSnareDrum (MIT)

  • Header: Drums/synthsnaredrum.h
  • API: Init(sr), SetFreq(f), SetSnappy(s), SetDecay(d), Trig(), Process(trigger_bool).

5. Physical Modeling Synthesis

StringVoice (MIT)

  • Header: PhysicalModeling/stringvoice.h
  • Origin: Mutable Instruments Rings / Plaits.
  • API: Init(sr), SetFreq(f), SetAccent(a), SetStructure(s), SetBrightness(b), SetDamping(d), SetSustain(bool), Trig(), Process(trigger_bool).

ModalVoice (MIT)

  • Header: PhysicalModeling/modalvoice.h
  • Origin: Mutable Instruments Rings / Plaits.
  • API: Init(sr), SetFreq(f), SetAccent(a), SetStructure(s), SetBrightness(b), SetDamping(d), SetSustain(bool), Trig(), Process(trigger_bool).

Resonator (MIT)

Drip (MIT)

6. Dynamics & Sampling

Limiter (MIT)

  • Header: Dynamics/limiter.h
  • API: Init(), ProcessBlock(float *in, size_t size, float pre_gain).

CrossFade (MIT)

  • Header: Dynamics/crossfade.h
  • Curves: CROSSFADE_LIN, CROSSFADE_CPOW, CROSSFADE_LOG, CROSSFADE_EXP.
  • API: Init(curve), SetPos(pos) (\(0.0 - 1.0\)), Process(in1, in2).

GranularPlayer (MIT)

  • Header: Sampling/granularplayer.h
  • API: Init(float* sample, int size, float sample_rate), Process(float speed, float transposition, float grain_size).

Compressor (LGPL)

Balance (LGPL)