curl --request POST \
  --url https://api.musicgpt.com/api/public/v1/Cover \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: multipart/form-data' \
  --form audio_url=https://example.com/audio.wav \
  --form voice_id=demo-voice-id \
  --form pitch=0 \
  --form webhook_url=https://example.com/callback \
  --form audio_file=@example-file

{
  "success": true,
  "task_id": "b329c0df-b2eb-4914-b707-4d7dce53577e",
  "conversion_id": "16708396-da86-4a9e-9b90-66f774cc2382",
  "eta": 33
}