This is TouchString

Polyphonic physical modeling string synthesizer for the Synthux Touch synthesizer and Daisy Seed.

Quick Install

Flash the precompiled TouchString.bin (v2.1.0) directly using the Daisy Seed web programmer.

Controls

Pads

• P00 - Keyboard Octave Down (steps down up to -2 octaves) | Tap both P00 + P02 to reset to unison (0)
• P01 - String Dampen / Palm-Mute Choke (squeeze to damp ringing strings, tap to mute)
• P02 - Keyboard Octave Up (steps up up to +2 octaves) | Tap both P00 + P02 to reset to unison (0)
• P03...P09 - Note pads (strings 1 to 7)
• P10 (TO) - Tap tempo & Modifier:
  • Tap P10 in rhythm to set arpeggiator tempo (40–240 BPM)
  • Hold P10 + P00 - Tempo down
  • Hold P10 + P02 - Tempo up
  • Hold P10 + S33 - Pattern Shift
  • Hold P10 + S35 - Reverb Mix
  • Hold P10 + S36 - External Audio Input Volume
• P11 (CH) - Modifier | Hold for scale and voice mode selection:
  • P11 + P00 - Previous scale (cycles through all 7 scales)
  • P11 + P02 - Next scale (cycles through all 7 scales)
  • P11 + P03...P09 - Direct scale select (P03: Amara, P04: Oxalis, P05: Pigmy, P06: Major, P07: Natural Minor, P08: Minor Pentatonic, P09: Major Pentatonic)
  • P11 + P01 - Poly / Mono toggle (LED double-blink = Mono, single blink = Poly)
• P10 + P11 (TO + CH) - Hold both together for ~0.5s to recalibrate touch pad baselines (3 rapid blinks)

Knobs (clockwise)

• S30 Brightness | Exciter filter cutoff & string brightness
• S31 Pitch | Global tuning across ±1 octave (center = unison)
• S32 Timbre | String structure / harmonic content
• S33 Density | Arpeggiator pattern density (Hold TO: Pattern Shift)
• S34 Notes | Arpeggiator pitch randomization (chance of octave jumps & random scale notes)
• S35 String | Per-note acoustic timbre variation (randomizes brightness, structure, damping) | Hold TO: Reverb Mix

Faders

• S36 (left) Drive / Volume | Pull down to soften plucks and fade to quiet mute; push up for warm overdrive (Hold TO: External Input Gain)
• S37 (right) Damp | String sustain decay time (Hold TO: Reverb Mix)

Switches

• Left Switch — Exciter Mode

  • Up: Pluck (velocity-sensitive, soft tap to snappy strike)
  • Center: Pluck + Bow on hold (squeeze pad to swell into singing bowed sustain)
  • Down: Bow (continuous violin-like bowing & scratch sensitivity)

• Right Switch — Arpeggiator

  • Up: Latched (hands-free arpeggio loop)
  • Center: Momentary (arpeggiates while holding pads)
  • Down: Off

Polyphony & Expression

• Poly / Mono Modes: Toggle with P11 + P01. In Poly mode, all 7 strings run in stereo. In Mono mode, notes have last-note priority with centered stereo panning and smooth portamento.
• Pluck + Bow Arpeggiator: In Mode 1 (Left Switch center), holding a chord lets you bow a singing background chord while the arpeggiator plucks through the notes over top.
• Bowed Arpeggiator: In Bow mode (Left Switch down), the arpeggiator plays smooth bowed notes in sequence (stereo bariolage in Poly mode, singing legato in Mono mode).
• Keyboard Octaves & Bass Drones: Tapping P00 or P02 shifts the keyboard for new notes without interrupting currently held notes. You can hold a low bass drone with one hand, shift octaves, and pluck high melodies over it.
• String Dampen (P01): Squeeze P01 for acoustic palm-muting across all strings, or tap it to silence resonance.
• Velocity Sensitivity: Responsive touch tracking from whisper-quiet soft plucks to bright, punchy fortissimo.
• Aftertouch: In Pluck mode, gently rocking a held pad adds subtle acoustic finger vibrato. In Bow mode, pad pressure modulates bow friction and timbre.

Scales

Hold P11 (CH) and tap a note pad to jump directly to any scale, or use P00 / P02 to cycle:

• P03 — Amara: Celtic minor handpan tuning (C3, G3, Bb3, C4, D4, Eb4, G4)
• P04 — Oxalis: Folk major handpan tuning (C3, E3, F3, G3, A3, C4, F4)
• P05 — Pigmy: Dorian Pygmy minor tuning (C3, D3, Eb3, G3, Bb3, C4, Eb4)
• P06 — Major: Diatonic Major (C3, D3, E3, F3, G3, A3, C4)
• P07 — Natural Minor: Diatonic Minor (C3, D3, Eb3, F3, G3, Ab3, C4)
• P08 — Minor Pentatonic: Blues & folk (C3, Eb3, F3, G3, Bb3, C4, Eb4)
• P09 — Major Pentatonic: Bright & sweet (C3, D3, E3, G3, A3, C4, D4)

LED Indicator

The onboard LED provides rich visual feedback:

• Visual Tempo Pulse: When arpeggiator is active:
  • Momentary Arp: Pulses ON in rhythm with each quarter-note beat.
  • Latched Arp: Solid ON, dipping OFF briefly with each quarter-note beat.
• Scale Confirmation: Blinks $N$ times corresponding to scale 1 through 7 (Amara = 1 blink, ..., Major Pentatonic = 7 blinks).
• Octave Shift:
  • Unison (0): 1 solid medium confirmation blink
  • +1 / +2 Octaves: 2 or 3 quick crisp blinks
  • -1 / -2 Octaves: 1 or 2 slow pulses
• Voice Mode: Double blink = Mono, single long blink = Poly.
• Tap Tempo: Flashes instantly on valid taps to confirm tempo sync.
• Recalibration: 3 rapid blinks confirm capacitive sensor baseline reset.

Project Structure

TouchString/
├── TouchString.cpp      # Main application entry point
├── Makefile             # Build configuration
|-- common               # Configuration and utilities
├── string/              # Instrument core
├── touch/               # Simple Touch wrapper (pads, knobs, switches)
├── ui/                  # UI connecting instrument core with touch wrapper
└── lib/                 # Libraries
    ├── libDaisy/        # Daisy hardware abstraction
    └── DaisySP/         # DSP library

Project Setup

$ git clone --recurse-submodules https://github.com/Synthux-Academy/TouchString.git
$ make libs -j8
$ make clean; make -j8

Configuration

Edit config.h to customize the instrument.