Triggering

Triggering synchronizes the display to specific events in the audio signal so periodic waveforms hold still instead of rolling or jittering. OSC-1 has three independent trigger systems, each aimed at a different display:

How triggering works

A trigger watches the incoming signal for a defined event — usually the signal crossing a level in a chosen direction. Each time the event fires, the display restarts drawing from that point. Because the restart always happens at the same phase of the waveform, successive frames line up and the image appears frozen in place.

Two supporting controls appear throughout and are worth understanding once:

• Hysteresis — a noise margin around the trigger level. The signal must travel past the level by this much before a new trigger can fire, which stops noisy signals from re-triggering rapidly ("jitter"). Raise it if the image trembles; lower it if quiet signals fail to trigger.
• Holdoff — a minimum gap (in audio samples) between triggers. After a trigger fires, further triggers are ignored for this many samples. Useful for complex waveforms that cross the level several times per cycle: set holdoff to roughly one cycle so only the first crossing counts.

XY Trigger

Synchronizes the main XY display to a threshold crossing on one channel. Use it for Lissajous figures, oscilloscope music, or any time you want a "still" image instead of rolling visuals.

• ON / OFF — master toggle for the XY trigger.
• Channel — which signal is watched for the trigger event:
  • X — the left channel (horizontal deflection)
  • Y — the right channel (vertical deflection)
  • MID — the L+R mono sum, useful when neither channel alone is periodic
• Slope — the crossing direction that counts: RISING, FALLING, or ANY.
• Threshold (−100% to +100%) — the signal level the channel must cross. 0% triggers at the zero crossing, which suits most material.
• Holdoff (0–1024 samples) — minimum samples between triggers. The default 256 is about 5 ms at 48 kHz.
• Hysteresis (0–50%) — noise margin, default 2%.

Audio Trigger

Triggers the time-domain views on amplitude events. Use it for drum patterns, percussive audio, or beat-reactive content.

• ON / OFF — master toggle.
• Mode:
  • ZERO — triggers when the signal crosses zero. Level-independent; best for sustained periodic material.
  • LEVEL — triggers when the signal crosses the Level slider's value. Best for transients and percussive hits, where you want to catch the attack rather than every zero crossing.
• Slope — RISING, FALLING, or ANY.
• Level (−100% to +100%) — the amplitude to trigger on (used by LEVEL mode).
• Holdoff (0–1024 samples) and Hysteresis (0–50%) — as described above.

Sweep Trigger

The XY Sweep visualizer is a traditional time-sweep oscilloscope, and it has the most capable trigger of the three — including a spectral mode that locks to the music's pitch automatically. Configure it in Settings (⌘K) → VISUALIZERS under XY SWEEP (the sweep itself toggles there, or with the SWEEP button in the visualizer strip).

Shared sweep controls:

• Window Unit — what each of the 10 horizontal divisions measures:
  • TIME — a fixed duration per division (the classic scope behavior).
  • CYCLES — a number of wavelengths per division. In SPECTRAL or CUSTOM trigger mode the wavelength follows the detected (or chosen) pitch, so the waveform always fills the same fraction of the display no matter what note is playing; in LEVEL mode it uses the transport's reference frequency.
• Time/Div (0.1–100 ms) or Cycles/Div (0.1–8) — the size of one division in the selected unit.
• Channel — LEFT or RIGHT: the channel that is both displayed and used for triggering.

Trigger Mode: LEVEL

Classic edge triggering, like a hardware scope:

• Trigger Level (0–100%) — amplitude threshold.
• RISING / FALLING — which edge of the crossing fires the trigger.

Trigger Mode: SPECTRAL

Finds the main pitch of what is playing and locks the sweep to it. The waveform stays still even as the pitch moves, and the detected pitch is shown live in the sweep's lower-left readout as frequency and note — for example TRIG 75.2 Hz (D2). While the detector is searching it shows Detecting....

• Threshold (1–50%) — minimum spectral strength a candidate fundamental needs before the detector locks on. Raise it to ignore quiet or noisy passages.
• Phase Offset (0–360°) — rotates where in the waveform's cycle the sweep starts. Turn it to slide the displayed waveform left or right until the feature you care about sits where you want it.
• Stability (0–90%) — how reluctant the detector is to jump to a new pitch. Higher values keep the readout steady on complex material (it waits for a new pitch to persist before re-locking); lower values follow fast pitch changes more eagerly.

Trigger Mode: CUSTOM

Spectral phase-locking at a frequency you choose instead of auto-detection — useful when you know the signal's pitch, or want to watch one component of a chord:

• Custom Freq (20–2000 Hz) — the lock frequency, with quick presets A4 (440 Hz), C4 (261.63 Hz), 100, 200, and 1k.
• Phase Offset and Stability — as in SPECTRAL mode.

Which trigger should I use?

• Watching oscilloscope music or Lissajous art on the XY display → XY Trigger, channel X, slope RISING, threshold 0%.
• Watching a waveform that rolls or swims in the sweep → Sweep SPECTRAL mode; it needs no tuning for most musical material.
• Watching drums or transients → Audio Trigger in LEVEL mode, with the level set just below the hit's peak and holdoff raised until each hit shows once.
• A known test tone → Sweep CUSTOM mode at the tone's frequency.