Parameter Automation

Automate audio parameters with sample-accurate timing from any js node with scheduled audio parameter messages.

They work with any audio node that has an audio parameter inlet (gain~, osc~, pan~, delay~, filters, etc.). When you drag from an audio signal outlet, the audio parameter inlets will turn blue to indicate that it can be automated.

Message Types

Set

Set a parameter value immediately, or at a specific time.

// Set immediately
send({ type: 'set', value: 0.5 });

// Set at a specific time (absolute by default)
send({ type: 'set', value: 0.5, time: 1.0 });

// Set at a relative time (n seconds from now)
send({ type: 'set', value: 0.5, time: 0.5, timeMode: 'relative' });

The time field uses absolute time by default, which works naturally with clock scheduling — pass { audio: true } for lookahead scheduling, then pass the time argument from the callback directly:

// Schedule a parameter change on beat 0 with audio-precise timing
clock.onBeat(0, (time) => {
  send({ type: 'set', value: 440, time });
}, { audio: true });

// Schedule at a specific bar position
clock.schedule('4:0:0', (time) => {
  send({ type: 'set', value: 880, time });
}, { audio: true });

Trigger

Trigger an attack-decay-sustain envelope.

// Trigger immediately
send({
  type: 'trigger',
  values: { peak: 1, sustain: 0.7 },
  attack: 0.02,  // seconds
  decay: 0.1
});

// Trigger at a precise time (for beat-synced envelopes)
send({
  type: 'trigger',
  values: { peak: 1, sustain: 0.7 },
  attack: 0.02,
  decay: 0.1,
  time
});

values.start defaults to 0. The attack and decay fields accept a number (seconds with linear curve) or a full config object { time, curve, ... } for custom curves. See the curve types section below.

Release

Trigger a release phase (ramp down from current value).

// Release immediately
send({ type: 'release', release: 0.3, endValue: 0 });

// Release at a precise time
send({ type: 'release', release: 0.3, endValue: 0, time });

Like attack/decay, the release field accepts a number (seconds) or a full config object.

Trigger + Release Example

A common pattern — trigger on noteOn, release on noteOff:

recv((m) => {
  if (m.type === 'noteOn') {
    send({
      type: 'trigger',
      values: { peak: 1, sustain: 0.7 },
      attack: 0.02,
      decay: 0.1
    });
  } else if (m.type === 'noteOff') {
    send({ type: 'release', release: 0.3, endValue: 0 });
  }
});

The adsr object wraps this pattern with convenient inlets for each parameter.

Curve Types

When you pass a number for attack, decay, or release, it uses a linear curve. For custom curves, pass an object with time and curve:

The full config object shape is { time, curve, timeConstant?, values? }:

// number shorthand — equivalent to { time: 0.02, curve: 'linear' }
attack: 0.02

// object form — specify a curve type
attack: { time: 0.1, curve: 'exponential' }

// targetAtTime — approaches the target asymptotically (never fully arrives)
// timeConstant controls speed: smaller = faster.
// Reaches ~63% of the way in one time constant.
// Defaults to time * 0.3 if omitted.
decay: { time: 0.3, curve: 'targetAtTime', timeConstant: 0.1 }

// valueCurve — custom shape from an array of values
attack: {
  time: 0.1,
  curve: 'valueCurve',
  values: [0, 0.05, 0.2, 0.5, 0.8, 0.95, 1.0]
}

// Full example: exponential decay with custom attack curve
send({
  type: 'trigger',
  values: { peak: 1, sustain: 0.7 },
  attack: {
    time: 0.1,
    curve: 'valueCurve',
    values: [0, 0.05, 0.2, 0.5, 0.8, 0.95, 1.0]
  },
  decay: { time: 0.2, curve: 'exponential' }
});

The values array defines the exact shape of the curve over the phase duration. Values are absolute (not normalized) — the first element is the start value and the last is the end value. Requires at least 2 values.

Compatible Nodes

Any audio node with an AudioParam inlet accepts scheduled messages. Common targets:

• gain~ — automate volume
• osc~ — automate frequency, detune
• pan~ — automate stereo position
• delay~ — automate delay time
• lowpass~, highpass~, etc. — automate filter cutoff/Q
• compressor~ — automate threshold, ratio, etc.

See Also

• Clock API — transport-synced scheduling with clock.schedule
• adsr — envelope generator that sends scheduled messages
• line~ — control-value ramp generator (signal-based alternative)