demos.lib

Demos library. Its official prefix is dm.

This library provides a collection of example DSP algorithms and demonstrations used to illustrate Faust features, syntax, and best practices. It includes simple oscillators, filters, effects, and synthesis examples useful for learning and testing.

The Demos library is organized into 7 sections:

• Analyzers
• Filters
• Effects
• Reverbs
• Generators
• Motion
• Hysteresis

References

• https://github.com/grame-cncm/faustlibraries/blob/master/demos.lib

Analyzers

---

(dm.)mth_octave_spectral_level_demo

Demonstrate mth_octave_spectral_level in a standalone GUI.

Usage

_ : mth_octave_spectral_level_demo(BandsPerOctave) : _
_ : spectral_level_demo : _ // 2/3 octave

Where:

• BandsPerOctave: number of spectral bands per octave

Test

dm = library("demos.lib");
no = library("noises.lib");
mth_octave_spectral_level_demo_test = no.noise : dm.mth_octave_spectral_level_demo(1.5);

---

(dm.)spectral_level_demo

Spectral level display, 2/3 octave. Synonym for mth_octave_spectral_level_demo(1.5).

Usage

_ : spectral_level_demo : _

Test

dm = library("demos.lib");
no = library("noises.lib");
spectral_level_demo_test = no.noise : dm.spectral_level_demo;

Filters

---

(dm.)parametric_eq_demo

A parametric equalizer application.

Usage:

_ : parametric_eq_demo : _

Test

dm = library("demos.lib");
no = library("noises.lib");
parametric_eq_demo_test = no.noise : dm.parametric_eq_demo;

---

(dm.)spectral_tilt_demo

A spectral tilt application.

Usage

_ : spectral_tilt_demo(N) : _ 

Where:

• N: filter order (integer)

Test

dm = library("demos.lib");
no = library("noises.lib");
spectral_tilt_demo_test = no.noise : dm.spectral_tilt_demo(4);

All other parameters interactive

---

(dm.)mth_octave_filterbank_demo, (dm.)filterbank_demo

Graphic Equalizer: each filter-bank output signal routes through a fader.

Usage

_ : mth_octave_filterbank_demo(M) : _
_ : filterbank_demo : _

Where:

• M: number of bands per octave

Test

dm = library("demos.lib");
no = library("noises.lib");
mth_octave_filterbank_demo_test = no.noise : dm.mth_octave_filterbank_demo(1);
filterbank_demo_test = no.noise : dm.filterbank_demo;

Effects

---

(dm.)cubicnl_demo

Distortion demo application.

Usage:

_ : cubicnl_demo : _

Test

dm = library("demos.lib");
no = library("noises.lib");
cubicnl_demo_test = no.noise : dm.cubicnl_demo;

---

(dm.)gate_demo

Gate demo application.

Usage

_,_ : gate_demo : _,_

Test

dm = library("demos.lib");
no = library("noises.lib");
stereoNoise = no.noise, no.noise;
gate_demo_test = stereoNoise : dm.gate_demo;

---

(dm.)compressor_demo

Compressor demo application.

Usage

_,_ : compressor_demo : _,_

Test

dm = library("demos.lib");
no = library("noises.lib");
stereoNoise = no.noise, no.noise;
compressor_demo_test = stereoNoise : dm.compressor_demo;

---

(dm.)xfer_ott_demo

Demo application for co.xfer_ott, the model of Xfer Records' OTT, with the plug-in's controls in its own units and at its defaults: Depth, Time, In/Out Gain and Upward/Downward strength, and per band (Low / Mid / High) Threshold, Gain and the two branch bypasses. Continuous controls are smoothed; Bypass switches the whole effect off for A/B comparison.

Usage

_,_ : xfer_ott_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
xfer_ott_demo_test = (os.tosc(220)*0.3, os.tosc(3000)*0.03) : dm.xfer_ott_demo;

---

(dm.)moog_vcf_demo

Illustrate and compare all three Moog VCF implementations above.

Usage

_ : moog_vcf_demo : _

Test

dm = library("demos.lib");
os = library("oscillators.lib");
monoOsc(freq) = os.tosc(freq);
moog_vcf_demo_test = monoOsc(440) : dm.moog_vcf_demo;

---

(dm.)wah4_demo

Wah pedal application.

Usage

_ : wah4_demo : _

Test

dm = library("demos.lib");
os = library("oscillators.lib");
monoOsc(freq) = os.tosc(freq);
wah4_demo_test = monoOsc(440) : dm.wah4_demo;

---

(dm.)crybaby_demo

Crybaby effect application.

Usage

_ : crybaby_demo : _

Test

dm = library("demos.lib");
os = library("oscillators.lib");
monoOsc(freq) = os.tosc(freq);
crybaby_demo_test = monoOsc(440) : dm.crybaby_demo;

---

(dm.)flanger_demo

Flanger effect application.

Usage

_,_ : flanger_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
flanger_demo_test = stereoOsc(440, 442) : dm.flanger_demo;

---

(dm.)phaser2_demo

Phaser effect demo application.

Usage

_,_ : phaser2_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
phaser2_demo_test = stereoOsc(440, 442) : dm.phaser2_demo;

---

(dm.)tapeStop_demo

Stereo tape-stop effect.

Usage

_,_ : tapeStop_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
tapeStop_demo_test = stereoOsc(440, 442) : dm.tapeStop_demo;

Reverbs

---

(dm.)freeverb_demo

Freeverb demo application.

Usage

_,_ : freeverb_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
freeverb_demo_test = stereoOsc(440, 442) : dm.freeverb_demo;

---

(dm.)springreverb_demo

Mono spring-inspired reverb demo using re.springreverb.

Usage

_ : springreverb_demo : _

Test

dm = library("demos.lib");
os = library("oscillators.lib");
monoOsc(freq) = os.tosc(freq);
springreverb_demo_test = monoOsc(220) : dm.springreverb_demo;

---

(dm.)stereo_reverb_tester

Handy test inputs for reverberator demos below.

Usage

_,_ : stereo_reverb_tester(gui_group) : _,_

Where:

• gui_group: accepted for compatibility and ignored: the tester controls appear at the top level of the GUI, and every older call compiles, including stereo_reverb_tester(!) and the bare process = dm.stereo_reverb_tester; (three inputs, the first unused). (dm.)fdnrev0_demo puts the same controls in its own group.

Test

dm = library("demos.lib");
no = library("noises.lib");
stereoNoise = no.noise, no.noise;
stereo_reverb_tester_test = stereoNoise : dm.stereo_reverb_tester(_);

---

(dm.)fdnrev0_demo

A reverb application using fdnrev0.

Usage

_,_ : fdnrev0_demo(N,NB,BBSO) : _,_

Where:

• N: feedback Delay Network (FDN) order / number of delay lines used = order of feedback matrix / 2, 4, 8, or 16 [extend primes array below for 32, 64, ...]
• NB: number of frequency bands / Number of (nearly) independent T60 controls / Integer 3 or greater
• BBSO : butterworth band-split order / order of lowpass/highpass bandsplit used at each crossover freq / odd positive integer

Test

dm = library("demos.lib");
no = library("noises.lib");
stereoNoise = no.noise, no.noise;
fdnrev0_demo_test = stereoNoise : dm.fdnrev0_demo(16, 5, 3);

---

(dm.)zita_rev_fdn_demo

Reverb demo application based on zita_rev_fdn, with an 8-channel input bus and an 8-channel output bus.

Usage

si.bus(8) : zita_rev_fdn_demo : si.bus(8)

Test

dm = library("demos.lib");
os = library("oscillators.lib");
monoOsc(freq) = os.tosc(freq);
zita_rev_fdn_demo_test = par(i, 8, monoOsc(440 + i)) : dm.zita_rev_fdn_demo;

---

(dm.)zita_light

Light version of dm.zita_rev1 with only 2 UI elements.

Usage

_,_ : zita_light : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
zita_light_test = stereoOsc(440, 442) : dm.zita_light;

---

(dm.)zita_rev1

Example GUI for zita_rev1_stereo (mostly following the Linux zita-rev1 GUI). The Wet/Dry Mix follows the zita-rev1 mix law: with m = (1 - mix)/2, the dry gain is 1 - m^2 and the wet gain 0.7 m (2-m)/sqrt(t60m). The defaults are those of zita-rev1; as there, the equalizer bandwidths are fixed (no Q control).

Only the dry/wet and output level parameters are "dezippered" here. If parameters are to be varied in real time, use smooth(0.999) or the like in the same way.

Usage

_,_ : zita_rev1 : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
zita_rev1_test = stereoOsc(440, 442) : dm.zita_rev1;

References

• http://www.kokkinizita.net/linuxaudio/zita-rev1-doc/quickguide.html

---

(dm.)vital_rev_demo

Example GUI for vital_rev with all parameters exposed.

Usage

_,_ : vital_rev_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
vital_rev_demo_test = stereoOsc(440, 442) : dm.vital_rev_demo;

---

(dm.)reverbTank_demo

This is a stereo reverb following the "ReverbTank" example in [1], although some parameter ranges and scaling have been adjusted. It is an unofficial version of the Spin Semiconductor® Reverb. Other relevant instructional material can be found in [2-4].

Usage

_,_ : reverbTank_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
reverbTank_demo_test = stereoOsc(440, 442) : dm.reverbTank_demo;

References

• [1] Pirkle, W. C. (2019). Designing audio effect plugins in C++ (2nd ed.). Chapter 17.14.

• [2] Spin Semiconductor. (n.d.). Reverberation. Retrieved 2024-04-16, from http://www.spinsemi.com/knowledge_base/effects.html#Reverberation

• [3] Zölzer, U. (2022). Digital audio signal processing (3rd ed.). Chapter 7, Figure 7.39.

• [4] Valhalla DSP. (2010, August 25). RIP Keith Barr. Retrieved 2024-04-16, from https://valhalladsp.com/2010/08/25/rip-keith-barr/

---

(dm.)kb_rom_rev1_demo

Keith Barr reverb effect rom_rev1 demo application.

Usage

_,_ : kb_rom_rev1_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
kb_rom_rev1_demo_test = stereoOsc(440, 442) : dm.kb_rom_rev1_demo;

---

(dm.)dattorro_rev_demo

Example GUI for dattorro_rev with all parameters exposed and additional dry/wet and output gain control.

Usage

_,_ : dattorro_rev_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
dattorro_rev_demo_test = stereoOsc(440, 442) : dm.dattorro_rev_demo;

---

(dm.)jprev_demo

Example GUI for jprev with all parameters exposed.

Usage

_,_ : jprev_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
jprev_demo_test = stereoOsc(440, 442) : dm.jprev_demo;

---

(dm.)greyhole_demo

Example GUI for greyhole with all parameters exposed.

Usage

_,_ : greyhole_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
stereoOsc(f1, f2) = monoOsc(f1), monoOsc(f2);
monoOsc(freq) = os.tosc(freq);
greyhole_demo_test = stereoOsc(440, 442) : dm.greyhole_demo;

Generators

---

(dm.)sawtooth_demo

An application demonstrating the different sawtooth oscillators of Faust.

Usage

sawtooth_demo : _

Test

dm = library("demos.lib");
monoOsc(freq) = os.tosc(freq);
os = library("oscillators.lib");
sawtooth_demo_test = dm.sawtooth_demo + monoOsc(110) * 0.001;

---

(dm.)virtual_analog_oscillator_demo

Virtual analog oscillator demo application.

Usage

virtual_analog_oscillator_demo : _

Test

dm = library("demos.lib");
virtual_analog_oscillator_demo_test = dm.virtual_analog_oscillator_demo;

---

(dm.)twin_osc_demo

TwinOsc - virtual analog synthesis with a time-varying comb filter.

Based on: "Virtual Analog Synthesis with a Time-Varying Comb Filter" D. Lowenfels, AES Convention 115, October 2003.

Usage

twin_osc_demo : _,_

Test

dm = library("demos.lib");
twin_osc_demo_test = dm.twin_osc_demo;

References

• https://www.researchgate.net/publication/325654284

---

(dm.)oscrs_demo

Simple application demoing filter based oscillators.

Usage

oscrs_demo : _

Test

dm = library("demos.lib");
oscrs_demo_test = dm.oscrs_demo;

---

(dm.)oscr_demo

Sine oscillator demo based on 2D vector rotation. Synonym for oscrs_demo.

Usage

oscr_demo : _

Test

dm = library("demos.lib");
oscr_demo_test = dm.oscr_demo;

---

(dm.)velvet_noise_demo

Listen to velvet_noise!

Usage

velvet_noise_demo : _

Test

dm = library("demos.lib");
velvet_noise_demo_test = dm.velvet_noise_demo;

---

(dm.)latch_demo

Illustrate latch operation. The three outputs are a sine signal, the latch control signal, and the sine sampled and held by the latch.

Usage

latch_demo : _,_,_

Example

One way to visualize it is:

echo 'import("stdfaust.lib");' > latch_demo.dsp
echo 'process = dm.latch_demo;' >> latch_demo.dsp
faust2octave latch_demo.dsp
Octave:1> plot(faustout);

Test

dm = library("demos.lib");
latch_demo_test = dm.latch_demo;

---

(dm.)envelopes_demo

Illustrate various envelopes overlaid, including their gate * 1.1. The eight outputs are the gate * 1.1, then the smoothEnvelope, ar, arfe, are, asr, adsr and adsre envelopes.

Usage

envelopes_demo : si.bus(8)

Example

One way to visualize it is:

echo 'import("stdfaust.lib");' > envelopes_demo.dsp
echo 'process = dm.envelopes_demo;' >> envelopes_demo.dsp
faust2octave envelopes_demo.dsp
Octave:1> plot(faustout);

Test

dm = library("demos.lib");
envelopes_demo_test = dm.envelopes_demo;

---

(dm.)fft_spectral_level_demo

Make a real-time spectrum analyzer using FFT from analyzers.lib. The input signal is passed through, its spectrum is displayed in bargraphs.

Usage

_ : fft_spectral_level_demo(N) : _

Where:

• N: FFT size (must be a power of 2 known at compile time)

Example

echo 'import("stdfaust.lib");' > fft_spectral_level_demo.dsp
echo 'process = dm.fft_spectral_level_demo(256);' >> fft_spectral_level_demo.dsp
Mac:
  faust2caqt fft_spectral_level_demo.dsp
  open fft_spectral_level_demo.app
Linux GTK:
  faust2jack fft_spectral_level_demo.dsp
  ./fft_spectral_level_demo
Linux QT:
  faust2jaqt fft_spectral_level_demo.dsp
  ./fft_spectral_level_demo

Test

dm = library("demos.lib");
no = library("noises.lib");
fft_spectral_level_demo_test = no.noise : dm.fft_spectral_level_demo(256);

---

(dm.)reverse_echo_demo

Multichannel echo effect with reverse delays, the nChans echo channels being panned to stereo.

Usage

_ : reverse_echo_demo(nChans) : _,_

Where:

• nChans: number of echo channels, an integer > 1 known at compile time

Example

echo 'import("stdfaust.lib");' > reverse_echo_demo.dsp
echo 'nChans = 3; // Any integer > 1 should work here' >> reverse_echo_demo.dsp
echo 'process = dm.reverse_echo_demo(nChans);' >> reverse_echo_demo.dsp
Mac:
  faust2caqt reverse_echo_demo.dsp
  open reverse_echo_demo.app
Linux GTK:
  faust2jack reverse_echo_demo.dsp
  ./reverse_echo_demo
Linux QT:
  faust2jaqt reverse_echo_demo.dsp
  ./reverse_echo_demo
Etc.

Test

dm = library("demos.lib");
no = library("noises.lib");
reverse_echo_demo_test = no.noise : dm.reverse_echo_demo(3);

---

(dm.)pospass_demo

Use Positive-Pass Filter pospass() to frequency-shift a sine tone. First, a real sinusoid is converted to its analytic-signal form using pospass() to filter out its negative frequency component. Next, it is multiplied by a modulating complex sinusoid at the shifting frequency to create the frequency-shifted result. The real and imaginary parts are output to channels 1 & 2. For a more interesting frequency-shifting example, check the "Use Mic" checkbox to replace the input sinusoid by mic input. Note that frequency shifting is not the same as frequency scaling. A frequency-shifted harmonic signal is usually not harmonic. Very small frequency shifts give interesting chirp effects when there is feedback around the frequency shifter.

Usage

_ : pospass_demo : _,_

Example

echo 'import("stdfaust.lib");' > pospass_demo.dsp
echo 'process = dm.pospass_demo;' >> pospass_demo.dsp
Mac:
  faust2caqt pospass_demo.dsp
  open pospass_demo.app
Linux GTK:
  faust2jack pospass_demo.dsp
  ./pospass_demo
Linux QT:
  faust2jaqt pospass_demo.dsp
  ./pospass_demo
Etc.

Test

dm = library("demos.lib");
os = library("oscillators.lib");
monoOsc(freq) = os.tosc(freq);
pospass_demo_test = monoOsc(440) : dm.pospass_demo;

---

(dm.)exciter

Psychoacoustic harmonic exciter, with GUI.

Usage

_ : exciter : _

Test

dm = library("demos.lib");
no = library("noises.lib");
exciter_test = no.noise : dm.exciter;

References

• https://secure.aes.org/forum/pubs/ebriefs/?elib=16939
• https://www.researchgate.net/publication/258333577_Modeling_the_Harmonic_Exciter

---

(dm.)vocoder_demo

Use example of the vocoder function where an impulse train is used as excitation. The vocoder output is duplicated on two outputs.

Usage

_ : vocoder_demo : _,_

Test

dm = library("demos.lib");
os = library("oscillators.lib");
no = library("noises.lib");
vocoder_demo_test = no.noise : dm.vocoder_demo;

---

(dm.)colored_noise_demo

A coloured noise signal generator.

Usage

colored_noise_demo : _

Test

dm = library("demos.lib");
colored_noise_demo_test = dm.colored_noise_demo;

Motion

Motion, gravity, and orientation demos based on motion helpers.

---

(dm.)shock_trigger_demo

Debounced shock trigger driving a tone. UI:

• [Auto Pulse] synths periodic impacts.
• [Pulse Rate] sets the tempo.
• [Axis Offset] trims the accelerometer input before HP/threshold.
• [High-pass], [Threshold], [Debounce] shape the trigger window.
• [Tone Frequency] sets the audible indicator driven by the shock gate.

Usage

shock_trigger_demo : _

Test

dm = library("demos.lib");
shock_trigger_demo_test = dm.shock_trigger_demo;

---

(dm.)projected_gravity_demo

Gravity projection mapped to a low-pass filter sweep. UI:

• [Auto Tilt] + [Tilt Rate]/[Tilt Depth] synthesize rocking.
• [Axis Offset] biases the axis.
• [Low-pass] controls smoothing before projection
• [Offset] sets the dead-zone.
• [Noise Level] sets bed loudness; projection modulates filter cutoff.

Usage

projected_gravity_demo : _

Test

dm = library("demos.lib");
projected_gravity_demo_test = dm.projected_gravity_demo;

---

(dm.)total_accel_demo

Total acceleration envelope mapped to noise amplitude. UI:

• [Auto Motion] + per-axis rates/depth synthesize movement; per-axis offsets bias inputs.
• [Threshold]/[Gain] set envelope detection.
• [Attack]/[Release] smooth it.
• Envelope scales the saw tone amplitude.

Usage

total_accel_demo : _

Test

dm = library("demos.lib");
total_accel_demo_test = dm.total_accel_demo;

---

(dm.)orientation6_demo

Six-axis orientation weights mapped to six tonal channels. UI:

• [Auto Orbit] + [Orbit Rate]/[Depth] synthesize a 3D path; X/Y/Z knobs add offsets.
• Six [Shape ...] knobs tighten/loosen each face’s lobe.
• [Smooth] sets response time.
• Each weight drives a distinct tone channel.

Usage

orientation6_demo : _,_,_,_,_,_

Test

dm = library("demos.lib");
orientation6_demo_test = dm.orientation6_demo;

---

(dm.)motion_wrapper_demo

End-to-end motion feature monitor built on motion.lib:

• Ingests six 3-axis IMUs (left arm, feet, back, right arm, head, stomach).
• Derives shock triggers, inclinometers, projected gravity, accel/gyro envelopes, six-face orientation weights per sensor, and raw/scaled axis taps.
• Exposes 92 outputs matching the motion.lib signal names, each gated by its own checkbox: an output whose checkbox is off is 0.

The 18 inputs are, in order: leftArm_x, leftArm_y, leftArm_z, feet_x, feet_y, feet_z, back_x, back_y, back_z, rightArm_x, rightArm_y, rightArm_z, head_x, head_y, head_z, stomach_x, stomach_y, stomach_z.

Usage

si.bus(18) : motion_wrapper_demo : si.bus(92)

Test

dm = library("demos.lib");
motion_wrapper_demo_test = dm.motion_wrapper_demo;

Hysteresis

---

(dm.)ja_transformer_demo

Magnetic transformer saturation demo using Jiles-Atherton hysteresis. Stereo processor with Pre-EQ, J-A hysteresis core, and inverse Post-EQ.

Usage

_,_ : ja_transformer_demo : _,_

Test

dm = library("demos.lib");
no = library("noises.lib");
stereoNoise = no.noise, no.noise;
ja_transformer_demo_test = stereoNoise : dm.ja_transformer_demo;

Pink Trombone

---

(dm.)pink_trombone_demo

Neil Thapen's Pink Trombone vocal-tract synthesiser (see pinktrombone.lib) with its original controls: voicebox (pitch, tenseness, always voice, pitch wobble), tract (tongue index/diameter, nasal) and two independent constrictions (index, diameter, active). As in the original, "always voice" is on by default, so the demo speaks on start-up.

Usage

pink_trombone_demo : _

Test

dm = library("demos.lib");
pink_trombone_demo_test = dm.pink_trombone_demo;