Start a music generation

Queues a song and returns 202 with the job. Poll GET /api/v1/music-generations/{id} until state is succeeded, failed, blocked or cancelled. A finished song is saved to your Files with the generated tag (if that save fails it is kept outside Files and output.file_id is null). On success, output.availability says whether it can be downloaded: ready means output.url is a signed download URL valid for 15 minutes (re-fetch the job for a fresh one); pending_scan means the saved file is still being scanned, so keep re-fetching the job (self-hosted installs can stay here for up to ~30 minutes); unavailable means the file was blocked or deleted and output.url will never be set, so stop polling. Credits for the model's price are reserved up front and settled on completion; a failed or cancelled job is not charged. A blocked job is not charged either, unless the provider generated the song before rejecting it and billed it: then the price is charged and credits.settled shows it. Send an Idempotency-Key header (1-255 printable ASCII characters) to make retries safe: a repeat with the same key and body returns the original job, and the same key with a different body is a 422 idempotency_key_reused. Omitted fields take the model defaults from GET /api/v1/music-models. Set organization_id to bill an organization you belong to, or null to bill your personal credits; omitted, the job bills your home organization (or your personal credits if you have none). Keys are scoped to the billed account, so the same key sent for a different organization_id starts a new job. An organization-billed API key always bills its own organization (see organization_id).