Vertical Mixing

Vertical mixing means changing the loudness of individual stems within a playing track — adding a percussion layer, muting a melody, or blending a full mix in response to gameplay events.

All vertical controls live on AudioTrackPlayer.

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Fading a stem by volume

AudioTrackPlayer player; // the track that's playing

// Fade "drums" to 50% of its maximum volume over 0.5 seconds
player.FadeVolume("drums", target: 0.5f, fade: 0.5f);

// Fade "melody" all the way out
player.FadeVolume("melody", target: 0f, fade: 1f);

// Restore "drums" to full volume
player.Play("drums", fade: 0.5f);

// Silence "drums" (same as FadeVolume to 0)
player.Mute("drums", fade: 0.5f);

FadeVolume's target is a 0–1 fraction, scaled by the stem's maximumVolume defined in the AudioTrack asset.

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Beat-synced stem control

Bring a stem in or out on the next metronome beat — keeps the mix change musically aligned.

// Fade "choir" in on the next beat
player.PlayOnBeat("choir", fade: 0.5f);

// Fade "choir" out on the next beat
player.StopOnBeat("choir", fade: 0.5f);

TIP

The track's BPM must be set for beat-sync to work. Without it the track has no metronome and the call fires immediately.

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Parameters

Parameters let you drive multiple stems from a single 0–1 value. Each stem has a curve that maps the parameter value to a volume target, so designers control the relationship — not programmers.

Define parameters in the AudioTrack asset's Parameters foldout. See Audio Tracks — Parameters for setup.

// Slide "tension" to 0.8 — every curve in the parameter is evaluated and faded
player.SetParameter("tension", value: 0.8f, fade: 0.5f);

// Tension eases off
player.SetParameter("tension", 0.2f, fade: 1f);

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Solo / unsolo

Isolate one stem for playback testing or dramatic effect:

// Silence everything except "bass"
player.SoloStem("bass", fade: 0.3f);

// Restore all stems to their isActive defaults
player.ClearSolo(fade: 0.3f);

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Emotional state

The most expressive vertical control is the emotional state system. Instead of manipulating individual stems, you move two abstract axes (e.g. Danger and Pace) and let a designer-authored asset translate those into stem volumes.

Setup

1. Create an AudioEmotionalState asset: Assets → Create → OCEAN → HYDRA → Emotional State

2. Name your axes — e.g. Axis A: Danger, Axis B: Pace.

3. Add a Stem Mapping for each stem in the track:

   • Stem ID — must match the stem ID in the AudioTrack.
   • Axis A Curve — volume factor as a function of axis A (x: 0–1, y: 0–1).
   • Axis B Curve — volume factor as a function of axis B.
   • Final volume = curveA(axisA) × curveB(axisB).

4. Assign the asset to the AudioTrackPlayer's Emotional State field.

Runtime

AudioTrackPlayer player; // has an AudioEmotionalState assigned

// High danger (0.9), medium pace (0.5) — 0.5s crossfade
player.SetEmotionalState(axisA: 0.9f, axisB: 0.5f, fade: 0.5f);

// Calm state — very low danger, slow pace
player.SetEmotionalState(0.1f, 0.1f, fade: 2f);

Both axes are clamped to [0, 1]. The call does nothing if no AudioEmotionalState asset is assigned.

Design example

AudioEmotionalState: CombatMix
  Axes: Danger / Pace

  Stem "drums":
    Axis A (Danger): flat 0 until 0.3, rises to 1 by 0.7
    Axis B (Pace):   linear 0→1

  Stem "strings":
    Axis A (Danger): linear 0→1
    Axis B (Pace):   constant 1

  Stem "bass":
    Axis A (Danger): sigmoid — near 0 below 0.5, near 1 above 0.5
    Axis B (Pace):   linear 0→1

  Stem "ambient_pad":
    Axis A (Danger): inverted — full at 0, silent at 1
    Axis B (Pace):   constant 1

At danger=0.9, pace=0.8: drums and bass are loud, strings are swelling, ambient pad is nearly silent. At danger=0.1, pace=0.1: only the ambient pad is audible — a quiet, tense moment.

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VerticalAudioTransition (trigger-based)

The VerticalAudioTransition component fires stem play/mute commands when a physics trigger is exited. Useful for environmental triggers — a player leaving a collider fades stems in or out.

Add it to a GameObject with a BoxCollider trigger:

Field	Description
Track Player	The AudioTrackPlayer to control.
Transitions	List of stem commands to fire on exit.

Each transition entry has:

Field	Description
ID	Stem ID to target.
State	Play or Stop.
Duration	Fade time in seconds.