Music Track

/music-track — Generate a Loop or Cinematic Music Track

Overview

ElevenLabs Music renders a track from a prompt. Summer clamps the requested length to 3–600 seconds before sending it, so anything outside that range is silently pulled to the nearest bound. Quality depends on prompt specificity: tempo (BPM), key, instrumentation, mood, structural cue. "Epic orchestral" returns generic stock music. "85 BPM, D minor, solo cello and detuned upright piano, sparse, melancholic, no drums, 4/4" returns a usable score for a melancholic exploration scene.

This skill produces one track aligned with the audio bible's music style and dynamic music plan, then wires it as an AudioStreamPlayer on the Music bus with a marked loop point if it's a loop, or as a linear cinematic stream if it's a one-shot.

When to use

• Looped track for a level, biome, menu, or game state (calm / tension / combat).
• Cinematic linear track for an intro, ending, boss reveal, or cutscene.
• Replacing a placeholder loop with on-bible music.

When NOT to use

• Short stings / event punctuation (<5s) → use sound-effect with class Stinger.
• Adaptive layered stems with state-driven crossfades → adaptive-music.
• Ambient bed with no melody → ambient-bed.

Steps

1. Read the audio bible

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Read .summer/audio-bible.md

The bible names the primary style, tempo range, key center, time signature, and the dynamic music model. This skill writes prompts that respect those numbers.

If no bible exists:

No .summer/audio-bible.md. Music without an audio bible drifts into stock-library territory. Run /audio-direction first, or I can ship a one-off with explicit defaults — your call.

2. Identify the track's role

Ask if not obvious:

Which slot in the dynamic music plan? Calm exploration, tension, combat, boss, victory, menu, ending, or one-off cutscene?

Each slot has different rules:

3. Build the prompt — tempo + key + instrumentation + mood + structural cue

Prompts that work:

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85 BPM, D minor, 4/4, solo cello and detuned upright piano, sparse, melancholic
exploration loop, no drums, gentle reverb, even dynamics, 60s

128 BPM, D dorian, 4/4, full orchestral combat, low brass ostinato, taiko drums
on 1 and 3, strings tremolo, urgent, no melodic resolution, 60s loop

90 BPM, A minor, 6/8, lo-fi exploration, vintage Rhodes electric piano,
tape hiss, warm bass, soft brushed snare, no vocals, 45s loop

70 BPM, F minor, 4/4, ambient menu loop, pad layer, distant choir, single
piano motif every 8 bars, no drums, 30s loop with seamless return

110 BPM, C minor harmonic, 4/4, dark synthwave boss intro, gated reverb snare,
arpeggiated bass synth, lead saw on melody, builds to cymbal swell at 0:50,
linear 60s, ends on sustained pad

Prompts that DON'T work (and why):

4. Tempo, key, instrumentation specifics that matter

Tempo (BPM) — name a single number, not a range. Music model interprets ranges as mid-point with drift. 85 BPM is better than 80–90 BPM.

Key — name mode (D minor, D dorian, D natural minor, C minor harmonic). The bible's modulation rules go here: combat tracks shift to dorian, calm tracks to natural minor.

Instrumentation — name 2–4 specific instruments, not sections. solo cello not strings. upright piano not keys. Rhodes electric piano not electric piano. The model's vocabulary is closer to a session musician's than a producer's.

Mood — concrete adjectives anchored to motion: melancholic and slow, urgent and driving, triumphant and rising. Avoid genre adjectives like epic, chill, hype.

Structural cue — for linear tracks, name the arc: builds at 0:30 to a hit at 0:50, decays. For loops, name the cell: 4-bar phrase repeats, instrument swap every 8 bars.

5. Loop vs cinematic decision

For loops: generate ≥30s, prefer 45–60s. Shorter loops are recognized as repetition within 90s of play and become annoying. The bible's "no state stays >90s without variation" rule means even a 60s loop should contain internal variation (instrument swap on alternating cycles).

For linear: generate ≥60s for cutscenes, up to 300s for endings. Ask for one rendered piece rather than splicing; the model handles long arcs.

6. Confirm and call

Show the prompt:

Prompt: 85 BPM, D minor, 4/4, solo cello and detuned upright piano, sparse, melancholic exploration loop, no drums, gentle reverb, 60s loop Duration 60s. This uses credits. Generate?

The music capability reads the description from prompt, not text — the mirror image of sound_effects. Without prompt the call is refused (prompt_required).

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assets.generate_audio({
  capability: "music",
  prompt: "85 BPM, D minor, 4/4, solo cello and detuned upright piano, sparse, melancholic exploration loop, no drums, gentle reverb, 60s loop",
  durationSeconds: 60
})
// Then: summer_import_from_url(url: "<asset.fileUrl>", path: "res://audio/music/calm_exploration.mp3")

durationSeconds is clamped to 3–600, and a longer track costs more: dryRun: true returns the estimate in credits first. Music comes back as MP3 (audio/mpeg), so a .mp3 target path is correct.

7. Mark the loop point in Summer Engine

ElevenLabs Music does not return a loop-clean cut. You must mark the loop point in Summer Engine's Import dock so playback returns to the loop point on completion, not to 0:00.

The MP3 importer exposes exactly five options — loop, loop_offset, bpm, beat_count, bar_beats. There is no loop_mode on MP3 or OGG; loop_mode belongs to the WAV importer, where it is spelled edit/loop_mode.

In audio/music/calm_exploration.mp3.import:

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[params]
loop = true
loop_offset = 0.0

If the start has a fade-in but the body is loopable, set loop_offset = 4.0 (4 seconds of intro skipped on loop, plays full track first time). bpm + beat_count + bar_beats are what you set if you want beat-synced transitions later — see adaptive-music.

For seamless looping, the cleaner option is to ask the model to generate a cell (one bar / one phrase) and concatenate; or generate at 60s and trust the model's structural cue. Crossfade looping in code is the practical fallback (step 9).

8. Wire it as AudioStreamPlayer on the Music bus

One script adds the player with its settings; scenePath is the exact scene to change:

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summer_run_script(scenePath="res://main.tscn", source="""
func run(ctx):
    ctx.add_node("AudioStreamPlayer", "MusicCalm", null, {
        "stream": load("res://audio/music/calm_exploration.mp3"),
        "bus": "Music",
        "volume_db": -8.0,
        "autoplay": true,
    })
    ctx.save_scene()
""")

Music is AudioStreamPlayer (not 2D / 3D) — non-positional. The bible's Music -8 dB mix sits the music behind SFX where it belongs.

9. Crossfade-loop pattern (no marked loop point)

If the loop click bothers the user, crossfade two players. Set loop = false in the import file first, so each player stops at the end.

gdscriptCopy code
# scripts/audio/MusicLoopCrossfade.gd
extends Node
@export var stream: AudioStream
@export var fade := 1.0
@export var volume_db := -8.0
var _players: Array[AudioStreamPlayer] = []
var _current := 0

func _ready() -> void:
	for i in 2:
		var p := AudioStreamPlayer.new()
		p.stream = stream
		p.bus = "Music"
		p.volume_db = volume_db
		add_child(p)
		_players.append(p)
	_players[0].play()

func _process(_delta: float) -> void:
	var a := _players[_current]
	if not a.playing or a.get_playback_position() < stream.get_length() - fade:
		return
	_current = 1 - _current
	var b := _players[_current]
	b.volume_db = -80.0
	b.play()
	var t := create_tween().set_parallel()
	t.tween_property(a, "volume_db", -80.0, fade)
	t.tween_property(b, "volume_db", volume_db, fade)
	t.chain().tween_callback(a.stop)

The next player starts fade seconds before the current one ends and the two cross over, so the seam is never heard.

Reference card — prompts by slot

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Calm explore (folk):    78 BPM, D minor, 6/8, fingerpicked acoustic guitar,
                        upright bass on 1, soft hand percussion, no melody on
                        first 8 bars, 60s loop

Tension (orchestral):   95 BPM, D dorian, 4/4, low strings sustained, single
                        timpani roll every 8 bars, sparse french horn motif,
                        no drums, 60s loop

Combat (orchestral):    140 BPM, D dorian, 4/4, taiko drums on 1 and 3,
                        ostinato low brass, strings tremolo, urgent and driving,
                        no melodic resolution, 60s loop

Boss (synthwave):       110 BPM, C minor harmonic, 4/4, gated snare, arpeggio
                        bass synth, lead saw on melody, builds at 0:50,
                        linear 60s

Menu (lo-fi):           70 BPM, F minor, 4/4, vintage Rhodes, tape hiss,
                        soft brushed snare, single piano motif every 8 bars,
                        45s loop

Cutscene (cinematic):   varies tempo, D minor, 4/4, solo piano opens,
                        strings enter at 0:20, full orchestra at 0:50,
                        decay to solo piano at 1:30, linear 120s

Anti-patterns

• Genre adjectives only. epic, chill, hype — meaningless.
• Naming a game or composer. Model won't replicate; use ingredients.
• Loop shorter than 30s. Recognized as repetition fast.
• Music on Master bus at 0 dB. Buries SFX. Use Music bus at -8 dB.
• Generating before reading the bible. Style drift.
• Skipping the loop-mark step. Music returns to 0:00 with a click on every loop.

Edge cases

• Clip is 50s but you wanted 60s. Either regenerate or extend by overlap-crossfading the last 5s onto the start in an audio editor.
• Loop click on every cycle. Use the crossfade pattern in step 9.
• Clip is too long. Trim the tail in the import dock with loop_offset, or in an audio editor.
• Track sounds nothing like the references. Re-read the bible; the prompt may be missing the anchor instrument. Add it explicitly.
• Track has unexpected vocals. Add no vocals, instrumental only to the prompt.

Without Summer Engine

In a session without Summer Engine tools (the assets profile; the summer-assets skill has the whole loop), do steps 1-6 and skip steps 7-9 (loop point, AudioStreamPlayer, crossfade script). Save the file where the person asked with out (the summer-assets skill says how), and tell them the path and format. For a loop track, tell them it is made to loop.

Fallback (no MCP)

Print the prompt and instruct the user to run via the Summer dashboard, then summer_import_from_url the rendered MP3.

Handoff

Track calm_exploration.mp3 wired to Game/MusicCalm on the Music bus, autoplay on. Next:

• Mark the loop point in the import dock if the bible calls for looped playback.
• Generate the tension and combat counterparts with /music-track again.
• To wire state-driven crossfades between calm / tension / combat, run /adaptive-music.

See also

• audio-direction — defines style, tempo, key, model
• adaptive-music — wiring stems to game state
• sound-effect — short stings
• ambient-bed — non-melodic location bed

From a shell

No Summer MCP tools in this session? Run each one as a command; when summer --version is missing or below 4.0, use npx -y summer-engine@latest in place of summer. Fields are flags in kebab-case (--scene-path res://main.tscn) or one --input '<json>', and summer ops describe <op> prints the exact input. The summer-cli skill has the rest.