The package description

Every package carries a short JSON description of its sounds, app2live/1. The SDKs write it from what you pass to send(); with the REST API you send it to POST /packages yourself.

{
  "schema": "app2live/1",
  "title": "Treinbeat",
  "source": { "app": "Web808", "app_version": "1.0.0", "platform": "web" },
  "tempo": { "bpm": 92 },
  "items": [
    { "id": "kick", "file": "kick.wav", "bytes": 1693484, "sha256": "…", "name": "Kick", "kind": "loop", "role": "drums", "length_beats": 16 },
    { "id": "robot", "file": "robot.wav", "bytes": 420112, "sha256": "…", "name": "Robot hallo", "kind": "oneshot", "role": "vocal" }
  ]
}

In Live this becomes a scene "Treinbeat (Web808)" with two tracks, "Kick (Web808)" and "Robot hallo (Web808)". The kick is a loop of 16 beats, warped at 92 BPM in Beats mode. The voice plays exactly as the app recorded it.

The package

Field
`schema`	Required: `"app2live/1"`.
`title`	The name of the scene, with the app after it, and of the folder on disk. Default "Untitled".
`source.app`	Added to every track name: "Kick (Web808)". Default "App".
`source.app_version`, `source.platform`	For your own use, and for support.
`tempo.bpm`	20 to 999: the tempo of every loop without a `bpm` of its own.
`items`	1 to 32 sounds, 200 MB together.

A sound

Field
`file`	Required. A letter or digit first, then letters, digits, space, `.`, `_` or `-`, ending in `.wav`, at most 100 characters, unique in the package.
`bytes`, `sha256`	Required by the server: the exact size of the file, and its SHA-256 in hex.
`kind`	`"loop"` or `"oneshot"`. Without it the sound is a one-shot, so always send it for a loop.
`name`	The name of the sound, at most 40 characters: letters of any language, digits, space and `_ - ( ) . ' & + # !`. Live adds the app name to the track: "Kick" becomes "Kick (Web808)", so never add it yourself. Default "Sound 1", by position.
`role`	`drums`, `bass`, `melodic`, `vocal`, `texture` or `fx`: it picks the warp mode of a loop.
`bpm`	The tempo of this loop, when it differs from `tempo.bpm`.
`length_beats`	The length of the loop in beats.
`warp_mode`	Overrides the role: `beats`, `tones`, `texture`, `repitch`, `complex` or `complex_pro`.
`color`	`"#RRGGBB"`; Live takes the nearest colour of its palette. Without it, all tracks of a package share one colour, and the next package gets the next one.
`gain_db`	The clip gain in dB, from -70 to +24.
`id`	Your own id, sent back with the result of this sound. Default: the position, from 1.

What LA2L does with it

A one-shot plays as it is: warp off, loop off.
A loop is warped and loops over its whole length. The warp mode follows the role: drums Beats, bass Tones, melodic and vocal Complex Pro, texture Texture, fx and no role Complex.
The tempo of a loop is its bpm, else tempo.bpm, else what length_beats and the length of the file give. Its length is length_beats, else what the tempo and the length of the file give, rounded to a whole beat when it is within 0.1 beat of one. Without any of these, Live guesses the tempo.
What LA2L does not know, it ignores, and says so in warnings: an unknown role, or a bpm on a one-shot. The package still goes through.

app2live-1.schema.json is the JSON Schema of a description as an app sends it.