Separate Stems

POST 
https://api.knoxstudio.ai/v1/music/stem-separation

Split a mix into stems (vocals, drums, bass, and so on). Latency scales with file length. Billed at $0.20 per minute of estimated duration. Multipart max 210MB. auto and 48 kHz MP3 ladders are not valid output_format values here.

Request

Query Parameters

Name	Type	Required	Description
output_format	String	No	Allowed: mp3_22050_32, mp3_24000_48, mp3_44100_32, mp3_44100_64, mp3_44100_96, mp3_44100_128, mp3_44100_192, pcm_8000, pcm_16000, pcm_22050, pcm_24000, pcm_32000, pcm_44100, pcm_48000, ulaw_8000, alaw_8000, opus_48000_32, opus_48000_64, opus_48000_96, opus_48000_128, opus_48000_192.

Request Headers

Name	Type	Required	Description
Authorization	String	Yes	Bearer <token> Knox API key. xi-api-key is also accepted.
Content-Type	String	Yes	multipart/form-data.

Request Body (multipart/form-data)

Name	Type	Required	Description
file	File	Yes	Mix to separate.
stem_variation_id	String	No	Stem variation preset.
sign_with_c2pa	Boolean	No	C2PA sign MP3 stems.

cURL Example

curl -X POST "https://api.knoxstudio.ai/v1/music/stem-separation?output_format=mp3_44100_128" \
     -H "Authorization: Bearer $KNOXCHAT_API_KEY" \
     -F "file=@mix.mp3" \
     -o stems.zip

Response

Success Response (200)

ZIP archive of stem audio files in the requested format.

Error Responses

Validation uses HTTP 422:

{
  "detail": [
    {
      "loc": ["body", "field"],
      "msg": "…",
      "type": "value_error"
    }
  ]
}

Other errors use { "detail": "message" }.

Status	When
400	WebSocket path called without Upgrade: websocket.
401	Missing or invalid API key.
402	Insufficient credits.
403	Token is not allowed to use this model.
404	Resource not found.
422	Validation error.
429	Rate limit exceeded.
500	Internal server error.