Remix an existing audio sample (a sound effect, ambiance, or music clip) into a variation guided by a text prompt, for example turning a track into an 80s synthwave or metal version. Both the sample and the prompt are required; the sample is uploaded as a URL or base64 audio and must be at most 15MB or the call returns HTTP 400, and duration must be one of the allowed values (0 means match the source, otherwise multiples of 10 up to 180 seconds). The job result is a single audio result containing the URL of an MP3 or WAV file (the URL's extension, .mp3 or .wav, says which). The optional modification_strength (0 to 1, default 0.6) controls how far the result departs from the original, and loop set to true makes the result loop seamlessly. Credits are held when the job is accepted and refunded if it fails or is cancelled. Use this to transform existing audio you already have; use createSoundEffect, createAmbiance, or createMusic to generate audio from scratch. Pass an optional request_id to tag the result so you can locate it later via listGenerations (type audio). Requires an API key (user scope). The call returns 202 with a job id - poll getApiJob (pass wait 30 to long-poll) honouring poll_after_ms, until status is succeeded; its result field is exactly the response documented for this operation. Synchronous responses are deprecated but still supported: pass `async: false` to block until the result is ready and receive it as the response body. Synchronous calls run on the same queue: the response carries an X-Ludo-Job-Id header, and a job still running after 15 minutes comes back as 202 with the job instead of an error. Each account may have up to 50 generations queued or running at once via the API; a request beyond that returns 429 (code PENDING_JOBS_LIMIT).