OMNi

4. ScratchDeck

A vinyl synthesizer – a gestural "turntable" with a curve bank, live-jog, and motion recorder.

ScratchDeck is a built-in Omni synthesizer emulating vinyl scratches (turntablism). Instead of a classic oscillator, you have a source sample (by default, an internal 200 → 2000 Hz chirp) and a needle motion curve, which the DSP sweeps across the sample during a note. One note = one scratch. Various components (needle position, speed, fader level) define the curves outlining the playhead's movement.

The engine is monophonic – maintaining the orthodoxy of a single DJ deck. Each subsequent note interrupts the previous one with an anti-click crossfade (64 samples, ≈ 1.3 ms @ 48 kHz), ensuring that rapid "baby → chirp → tear" sequences sound exactly like a real vinyl record.

Main Features

Curve Bank (12 slots)

The plugin stores 12 slots mapped directly across the chromatic scale. By default, you'll find turntablism classics there:

  • Baby – symmetrical forward/backward scratch.
  • Chirp – rapid peak-bounce (chirp).
  • Tear – a two-stage "torn" scratch.
  • Stab – a short, aggressive thrust.
  • Transformer – a rhythmic cut with the fader.
  • Crab, Flare, Twiddle – advanced patterns.

Playback Modes

  • Bank modeEach keyboard key selects a slot from the bank (e.g., C = Baby, C# = Chirp). Playback pitch is always natural. Perfect for live performances.
  • Transpose modeThe active slot is always played, but pitch depends on the played note. Ideal for composing melodic scratches in the Piano Roll.

Performance Tools

Live Jog – gesture pad

The JOG pad below the platter is your "hand on the vinyl". You drag horizontally with your mouse or finger:

  • Right (jog > 0) – you push the record forward (up to 5× speed).
  • Left (jog < 0) – you pull the record back (up to 3× speed reverse).
  • jog ≈ -0.25 – record halt (tape-stop).

The Jog adds to the curve – you can modify your designed motion on the fly.

Recorder – capturing gestures

Allows you to "teach" a new curve by executing a gesture:

  1. Press Record (Armed).
  2. Perform a gesture on the JOG pad. The first motion triggers recording (up to 600 frames).
  3. Press Stop. The gesture is automatically simplified by the Ramer-Douglas-Peucker algorithm (from ~200 to ~20 points).
  4. Save the curve to the active slot. It's instantly ready for MIDI playback!

Curve Editor

Click in an empty space to add a point. Drag points to modify the position curve for the active slot. Shift+Click removes a point. The engine receives these modifications in real-time without memory allocation on the audio thread!

MPE – Per-note Expression

Reads CLAP Note Expression / MPE for the active note:

  • Tuning (X) – pitch bend (ideal in Transpose mode).
  • Pressure (Z) – unipolar addition to the jog signal (hand pressure on the record).
  • Brightness (Y) – modulates the anti-aliasing strength of the low-pass filter.