Produce a piece of music from a text description, such as "epic orchestral battle theme" or "calm piano melody", with optional lyrics. Synchronous: the call blocks until generation finishes and returns a single audio result containing a URL; there is no separate polling step. The description field is required; duration must be one of the allowed values (0 means auto, otherwise multiples of 10 up to 180 seconds) and out-of-range values return HTTP 400. Credits are charged on success. Use this for songs and musical scores; use createSoundEffect for short sound effects, createAmbiance for looping background soundscapes, and createAudioTransform to remix an existing audio sample. Pass an optional request_id to tag the result so you can locate it later via getAudioResults. Requires an API key (user scope).