Hemiola
Sound Generator

Sound Generator

Sound Generator

The Sound Generator includes two independent synthesizers: SoundFont and Analog. It responds to the piano keyboard, USB/BT MIDI devices, the virtual interface, and MIDI Network (iOS/macOS). Audio buffer size is configurable for minimum latency.

MAIN

  • Master Volume: overall output level
  • Channel Volume: volume sent via MIDI CC 7
  • Pan: stereo panning (left ↔ right)
  • Stereo mode: select mono or stereo output
Note

A red dot appears on the top bar when clipping is detected. Lower the volume or activate the Limiter (Sound Effects) to resolve it.

PITCH

  • Master Tuning: fine-tune in cents (−100 to +100); the A4 reference frequency is displayed in Hz
  • Transpose: shift pitch by −12 to +12 semitones
  • A4 switch: emits a reference A4 tone, affected by Transpose and Master Tuning

AUDIO OUTPUT

  • Buffer Size: larger values reduce under-runs but increase latency
  • AUTO: automatic buffer size management (recommended in most cases)
Note

If the Sound Engine icon turns red, an audio buffer under-run occurred — increase the buffer size or enable AUTO. The section also shows a best-effort estimate of current audio latency and the sampling rate (set automatically by the audio engine).

SoundFont Synth

A sample-based synthesizer using the sf2 file format. Many free SoundFont collections are available online and can be uploaded to Hemiola.

  • Volume: output level of the SoundFont module
  • Pan: stereo panning of the SoundFont module
  • Current: select the active SoundFont file (when multiple are loaded)
  • Patch: select an instrument preset within the current SoundFont
  • Custom: upload a local .sf2 file to Hemiola

Analog Synth

A digital emulation of a classic analog synthesizer, loosely inspired by the Minimoog Model D.

  • Volume: output level of the Analog module
  • Pan: stereo panning of the Analog module

Analog Oscillators

All three oscillators share the same set of parameters:

  • Wave: waveform shape — Sine, Square, Sawtooth (×2), Triangle (×2), Pulse
  • Range: base octave — 32', 16', 8', 4', or 2'
  • Detune: fine-tune offset in cents (−100 to +100)
  • Shift: semitone offset (−12 to +12)
  • Volume: individual oscillator output level
  • PW: pulse width (duty cycle) — only affects the Pulse waveform. 50% = square wave, lower/higher values produce thinner pulses

Low Frequency Oscillator (LFO)

  • Route: Vibrato, Frequency (pitch), LPF Cutoff, or Stereo spread
  • Wave: waveform of the LFO (same types as oscillators)
  • BPM: oscillation frequency
  • Depth: amplitude range of the modulation

Low Pass Filter

A 4-pole (24 dB/oct) Moog Ladder filter applied per voice. At high emphasis the filter self-oscillates, producing a pitched tone.

  • Cutoff: frequencies above this threshold are attenuated
  • Emphasis: boosts frequencies around the cutoff frequency (resonance) — at maximum the filter self-oscillates
  • Amount: depth of filter envelope modulation (0 = none, 1000 = full sweep)
  • Kbd Track: keyboard tracking — how much the cutoff follows the played note (Off, 33%, 67%, 100%)
Note

LPF Cutoff can be modulated by the LFO (Route: LPF Cutoff) or by MIDI CC.

Filter Envelope

A dedicated per-voice ADSR envelope that sweeps the filter cutoff over time. The sweep range is controlled by Amount in the LPF section.

  • Attack: time (ms) for the filter to open after note-on
  • Decay: time (ms) to fall from the peak to sustain level
  • Sustain: cutoff level while key is held (per mille, 0–1000)
  • Release: time (ms) for the filter to close after note-off

Mono / Glide

When Mono is enabled, only one note sounds at a time. Held notes are tracked in a stack — releasing the current note returns to the previous one.

  • Mono: toggle between monophonic (one note) and polyphonic (multiple notes) modes
  • Priority: which note sounds when multiple keys are held — Low (lowest note wins), High (highest), or Last (most recent)
  • Retrigger: when on, envelopes restart on each new note; when off, the pitch changes smoothly without retriggering (legato)
  • Glide: portamento time (ms) — how long the pitch takes to slide between notes. 0 = instant
  • Drift: analog oscillator drift — adds subtle random pitch instability to each voice, simulating analog VCO behavior (0 = perfectly tuned, 100 = maximum warmth)
  • Voices: number of unison voices per note (1–8). Multiple voices are detuned symmetrically for a thicker sound. Only works in Mono mode
  • Detune: spread in cents between unison voices (0–50). Higher values create a wider, more detuned chorus effect

Noise Generator

  • White or pink noise oscillator — useful for adding breath, air, or texture to a sound. White noise has equal energy at all frequencies; pink noise has more bass energy (−3 dB/octave)
  • Type: White or Pink noise
  • Volume: output level of the noise

Loudness Envelope (ADSR)

Controls the amplitude envelope of the Analog synth. Uses exponential (RC) curves for a natural, analog-like response.

  • Attack: time (ms) to reach full amplitude after note-on
  • Decay: time (ms) to fall to the sustain level
  • Sustain: amplitude level while key is held (per mille, 0–1000)
  • Release: time (ms) to fade to silence after note-off