Music Track

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

Overview

ElevenLabs Music renders 10–300 seconds of music from a prompt. The output quality depends entirely 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 ( 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:

| Slot | Tempo | Energy | Instrumentation density | Loop or linear | |---|---|---|---|---| | Calm exploration | bible low end (e.g. 70–90) | Low | Sparse | Loop, ≥45s | | Tension | mid (e.g. 90–110) | Medium, no drums or sparse pulse | Adds one instrument | Loop, ≥45s | | Combat | high (e.g. 120–150) | High, full drums | Full | Loop, ≥45s | | Boss | high or low-and-menacing | Distinct from combat | Distinct, named instrument | Loop, ≥60s | | Victory sting | n/a | Resolution | n/a | Linear, 4–8s (use SFX skill instead) | | Menu / title | bible mid | Atmospheric | Anchor instrument | Loop, ≥30s | | Cutscene | varies | Linear arc | Varies | Linear, 60–180s | | Ending | varies | Linear arc with resolution | Varies | Linear, 60–300s |

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

Prompts that work:

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):

| Bad prompt | Failure mode | |---|---| | epic orchestral combat music | No tempo, no key, no instrumentation. Generic stock. | | Hollow Knight style track | The model can't reference IPs and won't try to clone style words. | | hopeful but sad menu music with strings and stuff | "Strings and stuff" is vague; model picks the wrong section. | | something for the boss fight | No tempo, no key, no mood vector. Random. | | loop (just the word) | No structure. Returns 30s of music that doesn't loop. |

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

| Choose loop when | Choose linear when | |---|---| | The slot plays for an unbounded time (level, menu, exploration) | The slot has a known length (cutscene, intro, ending) | | Player attention is on gameplay | Player attention is on the music | | You want to layer adaptive stems on top later | The arc is the point |

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. The model handles long arcs better than people expect; ask for one rendered piece rather than splicing.

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. Cost: ~12 credits. Generate?

summer_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
)
// Result: { asset: { fileUrl, ... } }
// Then: summer_import_from_url(url: "", path: "res://audio/music/calm_exploration.mp3")

durationSeconds range is 10–300.

7. Mark the loop point in Godot

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

In audio/music/calm_exploration.mp3.import:

[params]
loop = true
loop_offset = 0.0
loop_mode = 0  # 0=disabled, 1=forward, 2=ping-pong, 3=backward

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).

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 (see step 9).

8. Wire it as AudioStreamPlayer on the Music bus

summer_add_node(parentPath="/root/Game", type="AudioStreamPlayer", name="MusicCalm")
summer_set_prop(path="/root/Game/MusicCalm", property="stream", value="res://audio/music/calm_exploration.mp3")
summer_set_prop(path="/root/Game/MusicCalm", property="bus", value="Music")
summer_set_prop(path="/root/Game/MusicCalm", property="volume_db", value=-8.0)
summer_set_prop(path="/root/Game/MusicCalm", property="autoplay", value=true)

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, use a two-player crossfade:

# scripts/audio/MusicLoopCrossfade.gd
extends Node
@export var stream: AudioStream
@export var fade: float = 1.0
var _a: AudioStreamPlayer
var _b: AudioStreamPlayer
var _active: AudioStreamPlayer

func _ready() -> void:
	_a = _make_player()
	_b = _make_player()
	_active = _a
	_active.play()
	_active.finished.connect(_on_finished)

func _make_player() -> AudioStreamPlayer:
	var p := AudioStreamPlayer.new()
	p.stream = stream
	p.bus = "Music"
	p.volume_db = -8.0
	add_child(p)
	return p

func _on_finished() -> void:
	var next := _b if _active == _a else _a
	next.play()
	next.finished.connect(_on_finished, CONNECT_ONE_SHOT)
	_active = next

The next instance starts at 0:00 the moment the previous finishes — gapless.

Reference card — prompts by slot

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 (cheaper than you think) 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.

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

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: SummerEngine
• Source: SummerEngine/summer-engine-agent
• License: MIT
• Homepage: https://summerengine.com/

Install and usage instructions live in the source repository linked above.