> ## Documentation Index > Fetch the complete documentation index at: https://docs.slng.ai/llms.txt > Use this file to discover all available pages before exploring further. # Fish TTS S2.1 Pro > Synthesize speech with SLNG-hosted Fish TTS 2.1 Pro in a single HTTP request. The response is binary audio in the format set by `format` (MP3 by default). Send `application/json` to synthesize with a saved voice via `reference_id`, or `application/msgpack` to clone a voice from inline reference audio supplied in `references`. For incremental, low-latency synthesis, connect to the WebSocket channel at the same path instead. **Hosting: SLNG Sovereign Hosting.** Available in Netherlands, Germany, Australia, United Kingdom, Indonesia, Israel, India, Japan, Singapore, South Africa. Send requests to your region's gateway base URL: `https://eu-north.api.slng.ai`, `https://eu-west.api.slng.ai`, `https://au.api.slng.ai`, `https://gb.api.slng.ai`, `https://id.api.slng.ai`, `https://il.api.slng.ai`, `https://in.api.slng.ai`, `https://jp.api.slng.ai`, `https://sg.api.slng.ai`, `https://za.api.slng.ai`. ## OpenAPI ````yaml api-reference/openapi/tts-slng.oas.yaml POST /v1/tts/slng/fish/tts:s2.1-pro openapi: 3.0.3 info: title: SLNG Gateway API - SLNG TTS version: 0.1.0 description: Unified API for speech-to-text and text-to-speech services. contact: name: SLNG Support email: support@slng.ai servers: - url: https://eu-north.api.slng.ai description: 'Regional gateway: European Union (North) (eu-north)' - url: https://eu-west.api.slng.ai description: 'Regional gateway: European Union (West) (eu-west)' - url: https://au.api.slng.ai description: 'Regional gateway: Australia (au)' - url: https://gb.api.slng.ai description: 'Regional gateway: United Kingdom (gb)' - url: https://id.api.slng.ai description: 'Regional gateway: Indonesia (id)' - url: https://il.api.slng.ai description: 'Regional gateway: Israel (il)' - url: https://in.api.slng.ai description: 'Regional gateway: India (in)' - url: https://jp.api.slng.ai description: 'Regional gateway: Japan (jp)' - url: https://sg.api.slng.ai description: 'Regional gateway: Singapore (sg)' - url: https://za.api.slng.ai description: 'Regional gateway: South Africa (za)' security: - BearerAuth: [] tags: - name: Deepgram Aura 2 description: Deepgram Aura 2 for conversational voice agents. - name: Fish TTS 2.1 Pro description: >- SLNG-hosted Fish TTS 2.1 Pro over one-shot HTTP and native MessagePack WebSocket. paths: /v1/tts/slng/fish/tts:s2.1-pro: post: tags: - Fish TTS 2.1 Pro summary: Fish TTS 2.1 Pro description: > Synthesize speech with SLNG-hosted Fish TTS 2.1 Pro in a single HTTP request. The response is binary audio in the format set by `format` (MP3 by default). Send `application/json` to synthesize with a saved voice via `reference_id`, or `application/msgpack` to clone a voice from inline reference audio supplied in `references`. For incremental, low-latency synthesis, connect to the WebSocket channel at the same path instead. operationId: slng/fish/tts:s2.1-pro requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SlngFishTtsRequest' examples: basic: summary: Basic synthesis value: text: Hello from Fish Audio S2.1 Pro. reference_id: 9a9cf47702da476aa4629e2506d4a857 format: mp3 application/msgpack: schema: $ref: '#/components/schemas/SlngFishTtsRequest' examples: cloning: summary: Synthesis with inline reference audio (MessagePack only) value: text: Hello from Fish Audio S2.1 Pro. format: mp3 responses: '200': $ref: '#/components/responses/TtsSynthesisSuccess' '400': $ref: '#/components/responses/ProviderBadRequest' '401': $ref: '#/components/responses/ProviderUnauthorized' '402': $ref: '#/components/responses/ProviderPaymentRequired' '413': $ref: '#/components/responses/ProviderPayloadTooLarge' '415': $ref: '#/components/responses/UnsupportedMediaType' '503': $ref: '#/components/responses/ProviderServiceUnavailable' components: schemas: SlngFishTtsRequest: type: object description: >- Request body for SLNG-hosted Fish TTS 2.1 Pro synthesis. Shared by the `application/json` and `application/msgpack` content types; only MessagePack can carry inline reference audio in `references`. required: - text properties: text: type: string minLength: 1 description: >- Text to synthesize. S2-family variants support multi-speaker dialogue markers. reference_id: type: string description: >- Fish Audio voice-model ID. For multi-speaker synthesis, provide one ID per speaker as an array. references: type: array description: >- Inline reference audio for voice cloning. MessagePack-only, as the entries carry binary audio. items: $ref: '#/components/schemas/SlngFishTtsReference' prosody: type: object description: Prosody controls. properties: speed: type: number minimum: 0.5 maximum: 2 default: 1 description: Speech speed multiplier. volume: type: number minimum: -20 maximum: 20 default: 0 description: Volume adjustment in dB. normalize_loudness: type: boolean default: true description: Whether to normalize output loudness. temperature: type: number minimum: 0 maximum: 1 default: 0.7 description: Sampling temperature. top_p: type: number minimum: 0 maximum: 1 default: 0.7 description: Nucleus sampling probability mass. chunk_length: type: integer minimum: 100 maximum: 300 default: 300 description: Target chunk length for synthesis. normalize: type: boolean default: true description: Whether to normalize input text before synthesis. format: type: string enum: - wav - pcm - mp3 - opus default: mp3 description: Output audio format. sample_rate: type: integer nullable: true enum: - 8000 - 16000 - 24000 - 32000 - 44100 - 48000 description: >- Output sample rate in Hz. Defaults to the provider default for the chosen format when omitted. mp3_bitrate: type: integer enum: - 64 - 128 - 192 default: 128 description: MP3 bitrate in kbps (used when `format` is `mp3`). opus_bitrate: type: integer enum: - -1000 - 24000 - 32000 - 48000 - 64000 default: -1000 description: >- Opus bitrate in bps (used when `format` is `opus`). `-1000` selects the provider default. latency: type: string enum: - low - normal - balanced default: normal description: Latency/quality trade-off. max_new_tokens: type: integer default: 1024 description: Maximum number of new tokens to generate. repetition_penalty: type: number default: 1.2 description: Penalty applied to repeated tokens. min_chunk_length: type: integer minimum: 0 maximum: 100 default: 50 description: Minimum chunk length for synthesis. condition_on_previous_chunks: type: boolean default: true description: Whether generation is conditioned on previously generated chunks. early_stop_threshold: type: number minimum: 0 maximum: 1 default: 1 description: Early-stop threshold for generation. features: type: array description: Optional feature flags. items: type: string SlngFishTtsReference: type: object description: >- Inline reference audio for voice cloning. Supplied only over `application/msgpack`. required: - audio - text properties: audio: type: string format: binary description: Reference audio bytes (MessagePack binary value). text: type: string description: Transcript of the reference audio. AudioBinary: type: string format: binary description: Binary audio data. ProviderErrorResponse: type: object description: > Provider error response. Contains error information from the upstream provider. Common errors include invalid speakers, unsupported languages, or malformed requests. properties: error: type: string description: >- Error type or category (e.g., "TTS service error", "Validation error"). example: TTS service error status: type: number description: >- Original HTTP status code from the provider (may differ from gateway response code). example: 400 details: type: string description: > Detailed error message from the provider. For TTS errors, this typically includes the specific validation failure (e.g., invalid speaker ID for the selected model/language). example: >- Rime TTS API error: 400 Bad Request - Invalid argument: Invalid speaker: aurelie required: - error responses: TtsSynthesisSuccess: description: Synthesis successful. content: audio/*: schema: $ref: '#/components/schemas/AudioBinary' ProviderBadRequest: description: Bad request - invalid parameters provided. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' examples: validation-error: summary: Validation error value: error: Validation error details: 'Missing required field: text' ProviderUnauthorized: description: Invalid or missing API key. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' ProviderPaymentRequired: description: Insufficient credit or payment required. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' ProviderPayloadTooLarge: description: Request payload exceeds the provider size limit. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' UnsupportedMediaType: description: Unsupported request media type. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' ProviderServiceUnavailable: description: Service unavailable. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' securitySchemes: BearerAuth: type: http scheme: bearer description: | API key issued by SLNG. Pass as `Authorization: Bearer `. ````