Audio Tracks

AudioTrack

An AudioTrack is the central ScriptableObject. Everything playable in HYDRA starts here.

Assets → Create → OCEAN → HYDRA → Audio Track

Settings

Field	Type	Description
Group	AudioGroup	The mixer group this track routes to.
Loop	bool	Whether all stems loop.
BPM	float	Tempo used for beat-synced transitions. Set to 0 to disable.

Stems

Each entry in the Stems list is an AudioStem — one synchronized layer of the track.

Field	Type	Description
ID	string	Unique name for this layer, e.g. drums, bass, melody. Must be unique within the track.
Audio Clip	AudioClip	The default clip to play.
Maximum Volume	float	The volume ceiling when this stem is fully active (0–1).
Is Active	bool	Whether this stem starts playing. Inactive stems are silent until explicitly faded in.

Stem IDs

Every method that targets a specific stem takes its ID as a string. Keep IDs short and consistent — drums, bass, lead, sfx. They must match exactly (case-sensitive) in code and in AudioParameter and AudioEmotionalState assets.

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Clip variation

A stem can play more than one clip. There are two modes:

Random pool (multipleClips)

Toggle Multiple Clips on a stem and add clips to the list. On every Play of a non-looped stem, HYDRA picks one at random (uniform probability).

Stem: footstep
  ✓ Multiple Clips
  Clips: [step_a, step_b, step_c, step_d]

Weighted variation (useWeightedClips)

Toggle Weighted Variation for finer control. Each entry has a weight (0.01–10). Higher weight = picked more often. HYDRA uses history suppression to avoid the same clip playing back to back.

Field	Description
Weighted Clips	List of clip + weight pairs.
History Size	How many recently played indices to suppress before they can repeat. Default: 2.

Stem: ambient_bird
  ✓ Weighted Variation
  [crow.wav,  weight: 1]
  [robin.wav, weight: 3]   ← 3× more likely
  [jay.wav,   weight: 2]
  History Size: 2

Weighted vs Multiple Clips

If both toggles are on, weighted variation takes priority. Use weighted when probability control matters; use multiple clips for simple equal-chance variation.

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Parameters

Parameters let you map a single 0–1 float value to multiple stem volumes simultaneously, using an AnimationCurve per stem.

Add entries under the Parameters foldout on an AudioTrack.

Field	Description
Name	The parameter name used in code: player.SetParameter("tension", 0.8f).
Curves	One StemParameterCurve per stem. Each curve maps parameter value (X) to volume factor (Y).

Example — Tension parameter

Parameter: "tension"
  drums  → curve: flat at 0 until 0.3, then rises to 1
  strings → curve: linear 0→1
  choir  → curve: only audible above 0.7

In code:

trackPlayer.SetParameter("tension", 0.75f, fade: 0.5f);

This is more powerful than fading stems individually because all curves respond to a single value at once.

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Playing a track in code

// Get the player for a track that is already registered
AudioTrackPlayer player = AudioManager.Instance.GetAudioTrackPlayer(myTrack);

// Play all active stems with a 1-second fade
player.Play(fade: 1f);

// Play looped (forces loop = true on all stems)
player.PlayLooped(fade: 0.5f);

// Play once (forces loop = false, returns a CoRunner that completes when done)
CoRunner run = player.PlayOnce(fade: 0.5f);
run.OnComplete += () => Debug.Log("Track finished");

// Stop with a 2-second fadeout
player.Stop(fade: 2f);

// Stop immediately
player.ForceStop();

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Playing a specific stem

// Fade in one stem by ID
player.Play("melody", fade: 0.5f);

// Fade out one stem by ID
player.Mute("melody", fade: 0.5f);

// Mute all stems without stopping the AudioSources
player.Mute(fade: 1f);

// Set raw volume (0–1, scaled by the stem's maximumVolume)
player.SetVolume("drums", 0.5f);