Generate speech from text (Lightning V3.1)

<Warning>Endpoint scheduled for retirement. This URL will stop accepting requests 60 days from the Lightning v3.1 Pro launch (2026-05-15) — i.e. on 2026-07-14. The Lightning v3.1 model itself is current and stays. Migrate to POST /waves/v1/tts and select Lightning v3.1 via the model body field (default).</Warning>

Synthesize speech from text in a single request. The simplest way to get audio when you have the full text up front — pass text + voice_id, get back binary audio.

When to use this

• Use this for short utterances you can render before playback (notifications, prompts, batch jobs, audio file generation).
• Use the SSE streaming endpoint when you want playback to start before the full audio is ready (long passages, latency-sensitive apps).
• Use the WebSocket endpoint when text arrives incrementally (LLM token streams, live captioning).

Key features

• 44 kHz natural, expressive synthesis
• Cloned voice IDs (voice_*) work — same param as catalog voices
• 12 documented languages — see the model card for the full list
• Output formats: pcm, mp3, wav, ulaw, alaw
• Sample rates: 8 kHz – 44.1 kHz
• Speed: 0.5× – 2×
• Per-call pronunciation dictionaries via pronunciation_dicts

Examples

cURL

curl -X POST "https://api.smallest.ai/waves/v1/lightning-v3.1/get_speech" \
  -H "Authorization: Bearer $SMALLEST_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: audio/wav" \
  -d '{
    "text": "Hello from Lightning v3.1.",
    "voice_id": "magnus",
    "sample_rate": 24000,
    "output_format": "wav"
  }' --output speech.wav

Python (pip install smallestai>=4.4.0)

from smallestai import SmallestAI

client = SmallestAI(api_key="YOUR_API_KEY")

with open("speech.wav", "wb") as f:
    for chunk in client.waves.synthesize_lightning_v3_1(
        text="Hello from Lightning v3.1.",
        voice_id="magnus",
        sample_rate=24000,
        output_format="wav",
        # Optional: cloned voice support
        # voice_id="voice_FlPKRWI7DX",
        # Optional: pin pronunciations for specific words
        # pronunciation_dicts=["<your dict id>"],
    ):
        f.write(chunk)

JavaScript / TypeScript (using fetch)

const res = await fetch("https://api.smallest.ai/waves/v1/lightning-v3.1/get_speech", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.SMALLEST_API_KEY}`,
    "Content-Type": "application/json",
    Accept: "audio/wav",
  },
  body: JSON.stringify({
    text: "Hello from Lightning v3.1.",
    voice_id: "magnus",
    sample_rate: 24000,
    output_format: "wav",
  }),
});
const audio = Buffer.from(await res.arrayBuffer());
require("node:fs").writeFileSync("speech.wav", audio);

Common gotchas

• Set Accept: audio/wav. Omitting it can return an empty or unplayable response.
• Cloned voices (voice_* from add_voice) work on this endpoint and support pronunciation_dicts.
• pronunciation_dicts validates IDs at request time. Passing an unknown ID returns Invalid input data — create the dict first via the pronunciation-dicts endpoint and save the returned id.
• Pronunciation matching is case-sensitive. Add both Synopsis and synopsis if your text uses both casings.
• 44.1 kHz output is supported but most playback environments are happy with 24 kHz — drop the sample rate if bandwidth matters.
• JavaScript / TypeScript: the official smallestai npm package predates Lightning v3.1, so call this endpoint with fetch or axios as shown above.