Sync & Async Synthesis

Generate speech synchronously or concurrently — REST API and SDK examples.

Generate speech via the REST API or Python SDK — synchronously (one request, complete audio) or asynchronously (multiple requests in parallel).

Sample output (sync, voice: magnus):

Requirements

• An API key from the Smallest AI Console
• For Python: requests (or smallestai for the SDK)
• For JavaScript: Node.js 18+ (built-in fetch)

export SMALLEST_API_KEY="your-api-key-here"

Synchronous Text to Speech

Send text, receive complete audio in the response:

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" \
  -d '{
    "text": "Hello, this is a test of synchronous speech synthesis.",
    "voice_id": "magnus",
    "sample_rate": 24000,
    "output_format": "wav"
  }' --output sync_output.wav

Asynchronous Text to Speech

For concurrent requests (e.g., generating multiple audio files in parallel):

Python (asyncio)

import os
import asyncio
import aiohttp

API_KEY = os.environ["SMALLEST_API_KEY"]
URL = "https://api.smallest.ai/waves/v1/lightning-v3.1/get_speech"

async def synthesize(session, text, filename):
    async with session.post(URL, headers={
        "Authorization": f"Bearer {API_KEY}",
        "Content-Type": "application/json",
    }, json={
        "text": text,
        "voice_id": "magnus",
        "sample_rate": 24000,
        "output_format": "wav",
    }) as resp:
        audio = await resp.read()
        with open(filename, "wb") as f:
            f.write(audio)
        print(f"Saved {filename}")

async def main():
    async with aiohttp.ClientSession() as session:
        await asyncio.gather(
            synthesize(session, "First sentence.", "async_1.wav"),
            synthesize(session, "Second sentence.", "async_2.wav"),
            synthesize(session, "Third sentence.", "async_3.wav"),
        )

asyncio.run(main())

Parameters

Parameter	Type	Default	Description
text	string	required	Text to synthesize (max ~250 chars recommended)
voice_id	string	required	Voice to use (e.g., magnus, olivia, aarush)
sample_rate	int	44100	8000, 16000, 24000, or 44100 Hz
speed	float	1.0	Speech rate multiplier (0.5 to 2.0)
language	string	auto	Language code: en, hi, es, ta, or auto
output_format	string	pcm	Audio format: pcm, wav, mp3, or mulaw
pronunciation_dicts	array	—	List of pronunciation dictionary IDs

You can override any parameter per request:

# Override speed and sample rate for a single call
response = requests.post(URL, headers=headers, json={
    "text": "Fast and high quality.",
    "voice_id": "magnus",
    "speed": 1.5,
    "sample_rate": 44100,
    "output_format": "mp3",
})

When to Use Each Mode

• Synchronous: Real-time voice assistants, chatbot responses, single audio generation
• Asynchronous: Batch processing, generating multiple audio files, audiobook chapters, concurrent API calls

For real-time streaming where audio starts playing before generation completes, see Streaming TTS.

Need Help?

Check out the API Reference for the full endpoint specification, or ask on Discord.