> ## Documentation Index > Fetch the complete documentation index at: https://docs.rixapi.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Stem Layering > Layer an additional instrument track onto an existing song. > [!TIP] > > You can also submit through the unified task endpoint `POST /v1/task/submit` with `model` set to `suno/add-stem` and the parameters inside `input`. Both behave and bill the same. > [accordion] Task result > > What the fetch result holds once the task succeeds > > When the task succeeds, `data.musics` holds the tracks it produced, 2 per run. On partial success you are billed for the tracks that actually succeeded. > > ```json theme={null} > { > "code": "success", > "data": { > "task_id": "5adac6ee-...", > "action": "add-stem", > "model": "suno/add-stem", > "status": "SUCCESS", > "progress": "100%", > "submit_time": 1757800000000, > "finish_time": 1757800120000, > "musics": [ > { > "music_id": "89b20862-...", > "title": "Rain on Tin Roof", > "tags": "lo-fi piano", > "audio_url": "https://...", > "image_url": "https://...", > "duration": 187.56 > } > ] > } > } > ``` > > **music\_id** `string` *required* > > Track ID. Pass it to extend, cover, stem separation, export and other follow-up actions. > > **title** `string` > > Title. > > **tags** `string` > > Style tags. > > **lyrics** `string` > > Lyrics. Instrumentals do not include this field. > > **audio\_url** `string` > > Audio URL, downloadable directly. > > **image\_url** `string` > > Cover image URL. > > **image\_large\_url** `string` > > Large cover image URL. > > **video\_url** `string` > > Video URL. Omitted when there is no video. > > **duration** `number` > > Duration in seconds. ## OpenAPI ````yaml en/openapi/suno.json POST /suno/v2/add-stem openapi: 3.1.0 info: title: Suno API version: 1.0.0 description: Suno servers: - url: https://api.ephone.ai security: - bearerAuth: [] paths: /suno/v2/add-stem: post: summary: Stem Layering description: Layer an additional instrument track onto an existing song. operationId: suno_add_stem requestBody: required: true content: application/json: schema: type: object properties: mv: type: string enum: - chirp-v6 - chirp-v6-wild - chirp-v6-mini default: chirp-v6 description: >- **Model Version**: All three versions are priced the same; pick by the style you want. Options: `chirp-v6` v6 (default); `chirp-v6-wild` v6 Wild (bolder); `chirp-v6-mini` v6 Mini (faster). custom: type: boolean default: false description: >- **Custom Mode**: Off: describe the song in one line. On: supply your own full lyrics. gpt_description_prompt: type: string description: >- **Inspiration Prompt**: One line describing the song you want. Required when custom mode is off. Up to 3000 characters. prompt: type: string description: >- **Lyrics**: Full lyrics, up to 5000 characters. Use markers like [Verse] and [Chorus] to shape the structure. title: type: string description: '**Title**: Track title, up to 80 characters.' tags: type: string description: >- **Style Tags**: The style you want, e.g. 'lo-fi piano, mellow, rain'. Up to 1000 characters. negative_tags: type: string description: '**Avoid These Styles**: Styles to steer away from.' style_weight: type: number description: >- **Style Weight**: 0 to 1. Higher sticks closer to your style tags; lower leaves more room to improvise. weirdness_constraint: type: number description: >- **Weirdness**: 0 to 1. Higher yields more unexpected results; lower stays conventional. audio_weight: type: number description: >- **Audio Weight**: 0 to 1. How strongly the reference audio shapes the result. variety: type: string enum: - 'off' - normal - high - extra - max description: >- **Variety**: How far the result may drift from the style you specified. Options: `off` Exact; `normal` Balanced; `high` Varied; `extra` Bold; `max` Maximum. max_mode: type: boolean default: false description: >- **Max Quality**: Spend more compute to keep the whole song coherent. Custom mode only; doubles the price. model_id: type: string description: >- **Custom Model**: Generate with a model you trained. Use the model_id from a create-model result. Cannot be combined with persona_id. audio_format: type: string enum: - mp3 - m4a - wav description: >- **Output Format**: Format of the finished audio. Defaults to mp3. Options: `mp3` MP3 (common); `m4a` M4A; `wav` WAV (lossless). music_id: type: string description: >- **Source Track**: The track to work on. Use the music_id from an earlier result. notify_hook: type: string format: uri description: >- **Notify hook**: when the task ends, the same content as the fetch result is POSTed to this URL (a public http / https URL). Omit it to poll instead. required: - music_id example: mv: chirp-v6 custom: false music_id: track id responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/SubmitResponse' example: code: success message: success data: task_id: 5adac6ee-... '400': description: Bad Request content: application/json: schema: $ref: '#/components/schemas/Error' example: code: error message: music_id is required '401': description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/GatewayError' example: error: message: Invalid Token type: rix_api_error '429': description: Too Many Requests content: application/json: schema: $ref: '#/components/schemas/GatewayError' example: error: message: Too many requests, please try again later type: rix_api_error components: schemas: SubmitResponse: type: object properties: code: type: string enum: - success message: type: string data: type: object properties: task_id: type: string description: Task ID. required: - task_id required: - code - data Error: type: object properties: code: type: string message: type: string GatewayError: type: object properties: error: type: object properties: message: type: string type: type: string securitySchemes: bearerAuth: type: http scheme: bearer description: 'Send your API key in the `Authorization: Bearer YOUR_API_KEY` header.' ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.