This is TouchPulsar

Pulsar synthesizer for the Synthux Touch synthesizer and Daisy Seed, based on Curtis Roads' Sound Composition with Pulsars (2001). A single control sweeps from rhythm to tone and back. Below about 20 Hz each pulsar is heard as its own beat; above about 40 Hz the beats fuse into a pitched tone with a formant you can sweep like a filter.

Quick Install

Controls

Pads

Knobs (clockwise)

Faders

Switches

Pulsar Synthesis & Expression

• Rhythm ↔ Tone: Each pulse is a short burst (a pulsaret) followed by silence. The pulse rate is the pitch, or the tempo when slow. The burst length sets the formant, which works like a resonant filter, though no filter is involved.
• Three Formants: Spread adds two more formants above the main one, each panned by Width, for vowel-like and choral tones. Motion (P11 + S30) sets them drifting around the stereo field at slightly different speeds, and each pulsar is placed where its formant is at that moment, following Roads' per-formant spatial paths. In RHYTHM every pulse lands somewhere new; at audio rates it becomes a slow swirl. The main formant drifts too, so Motion is audible even with Spread at 0.
• Coupled / Free Formant: Coupled, the formant moves with the note, so the timbre stays the same across the keyboard. Free, it stays fixed in Hz, like a filter while the pitch moves underneath.
• Convolution: Each pulse triggers a copy of the sample filtered by the pulsaret, so the sample is replayed in the pulsar rhythm. Try short percussive sounds in RHYTHM and longer ones in FREE. A wooden knock is built in, and a hold on P01 records your own (input jack, up to 2 s).
• Live Input: Turn Shape fully right and the audio on the input jack becomes the pulsaret waveform. Each pulse opens a window onto the incoming sound, and every control applies: Window shapes the gate, Formant + Cluster set how long it opens, Mask and the switches chop the pattern, and Fold, Thick, Filter and Drive sit on top. In RHYTHM it's a tempo-synced gate/stutter; in TONE or FREE the fast gating turns into a pitched, ring-mod-like sound played from the pads. A note must be playing (pad, MIDI or Hold) for the input to be heard. Set the level with P11 + S35; while P11 is held, the LED lights when the input is loud enough. Careful with a microphone near speakers: it can feed back.
• Delay: Hold P11 and use S31/S32. S31 = time, synced to the tempo in 8 steps: 1/16, 1/8T, 1/8, 1/8. (default), 1/4T, 1/4, 1/4., 1/2. It follows tap tempo and MIDI clock and glides like tape when changed. S32 = amount: one knob for mix and feedback (0 = off; fully up = long, darkening repeats). The repeats ping-pong between left and right, and the Level fader still controls everything including the tails.
• Filter: Hold P11 and move the faders: right = cutoff, left = resonance. It's a smooth 12 dB/oct low-pass on both channels, placed before Drive so Drive saturates the resonance. At power-up it's fully open (no change to the sound).
• Chorus / Ensemble: Hold P10 and move the right fader. Lower half: a gentle two-voice stereo chorus. Upper half: a third voice fades in for a lush, string-machine ensemble. It sits after Drive, so it widens everything, including Thick, the filter, convolution and live input. Fully down = off.
• Thick: In TONE, the right fader doubles the pulsar train with a detuned copy, like two slightly out-of-tune oscillators: the sound gets wide, chorused and alive, and a sub-octave sine comes in at the top. The copy uses the same formants, shape and masking, so it keeps the pulsar character.
• Pressure: Pressing harder makes a note louder and pushes the formant up (set with Push). The sound follows the highest pressure of the last moment (the lift window, 0.15 s by default): pressing harder is heard at once, a quick finger lift is never heard, and a released note keeps its pre-lift pressure, for the release tail and with Hold. A slow, deliberate softening is still followed, one window behind. Tune the window with P11 + S34.
• Soft Takeover: When you hold P10, or after a MIDI CC changes a value, a knob only takes control once you move it, so values never jump.

Scales

Hold P11 (CH) and tap a note pad to jump directly to a scale, or use P00 / P02 to cycle. Hold P10 (TO) and tap a note pad to move the root (shown here in C).

LED Indicator

The onboard LED provides visual feedback:

• Pulsar Flash: In rhythm (below ~25 Hz), the LED flashes once for every pulsar that plays; masked pulsars stay dark, so you can see the burst pattern. At audio rates it stays on while a note sounds.
• Scale Confirmation: Blinks N times for scale 1 through 7 (Chromatic = 1 blink, …, Harmonic Minor = 7 blinks).
• Octave Shift: Quick blinks: 1 at unison, 2 at ±1, 3 at ±2, 4 at ±3 (in Chromatic, one more blink per 7-semitone step).
• Root Key: 1 blink.
• Tempo: A short flash on every P10 tap and on P10 + P00/P02.
• Hold / Convolution / Formant Mode: 2 blinks = on (coupled), 1 blink = off (free).
• Recording: Fast flashing while P01 records; 3 blinks when the sample is captured; 1 long blink if only silence was recorded (the old sample stays).
• Input Level: While P11 is held, the LED lights when the input signal is above about −26 dB, to help set P11 + S35.
• Recalibration: 3 rapid blinks confirm the touch sensor baseline reset.

MIDI

TouchPulsar appears as a USB MIDI device (listed as PulsarTouch in your computer or DAW) when connected via the Daisy Seed's USB port. It listens on all MIDI channels.

• Notes: Fully chromatic, separate from the pad scale. Pads and MIDI share one voice (last note wins). Notes follow the Range switch:
  • TONE: pitch
  • FREE: formant pitch (C3 = no transpose)
  • RHYTHM: white keys C to B pick 1/4 … 1/32 at C3, and each octave up doubles the rate
• Velocity: Note level. Aftertouch (channel or poly): same as pad pressure.
• Pitch Bend: ±2 semitones (CC 88 sets the range, 0–24).
• Glide: Applied only when you play legato. TONE: a short fixed portamento (60 ms). RHYTHM: set by the right fader.
• Sustain (CC 64): Holds released notes.
• MIDI Clock Sync: Automatic. When clock arrives, RHYTHM follows its tempo and locks the pulses to the beat. Start resets the beat. If the clock stops for more than 0.5 s, TouchPulsar goes back to its own tempo.

CC Map

Soft Takeover: A value set via MIDI CC is kept until the corresponding knob or fader is moved; from then on the physical control takes over again.

Project Structure

PulsarTouch/
├── PulsarTouch.cpp      # Main application entry point
├── Makefile             # Build configuration
├── common/              # Utilities
├── pulsar/              # Instrument core: pulsar engine + controls (platform-free)
├── touch/               # Simple Touch wrapper (pads, knobs, switches) from TouchString
├── ui/                  # UI connecting instrument core with touch wrapper, MIDI, LED
└── test/                # Host test: control checks + comparison with the browser engine

Project Setup

Needs the Daisy toolchain. libDaisy is a git submodule in daisy/lib/libDaisy (Synthux's fork, pinned to the version TouchString uses); DaisySP isn't needed. With a local source checkout and its submodules available, build from daisy/:

$ cd TouchPulsar/daisy
$ make libs -j8
$ make clean; make -j8
$ make program-dfu

• make DEBUG=1 prints audio CPU load over USB serial once a second (USB MIDI is off in this mode).
• make -C test checks the engine on your computer and compares its sound with the browser prototype in ../web.

Credits

• Pulsar synthesis: Curtis Roads, Sound Composition with Pulsars, Journal of the Audio Engineering Society, vol. 49, no. 3, March 2001.
• Touch drivers: Synthux Academy TouchString.