Text to Speech

The Text to Speech (TTS) service converts written text into spoken audio. The unified POST /tasks/audio/speech endpoint exposes two models:

orpheus-3b-tts (default) — multilingual, multi-speaker. Voices are catalog tags (e.g. salt_lug_0001); list them with GET /tasks/voice/speakers.
spark-tts — the six fixed Ugandan voices below; supports streaming on Modal.

Migrating? The legacy /tasks/tts, /tasks/modal/tts, /tasks/runpod/tts, /tasks/modal/orpheus/tts, streaming (/stream, /stream-with-url), Orpheus batch, speaker-listing, and refresh-url endpoints are deprecated. Use the unified /tasks/audio/speech endpoints below.

Single Synthesis (orpheus-3b-tts, default)

Parameters

Parameter	Type	Required	Description
`text`	string	Yes	The text to convert to speech.
`model`	string	No	`orpheus-3b-tts` (default) or `spark-tts`.
`voice`	string	Yes	Catalog tag (see `GET /tasks/voice/speakers`).
`language`	string	Yes	Required for `orpheus-3b-tts` — ISO code or full name.

import os
import requests
from dotenv import load_dotenv

load_dotenv()

url = "https://api.sunbird.ai/tasks/audio/speech"
access_token = os.getenv("AUTH_TOKEN")

headers = {
    "accept": "application/json",
    "Authorization": f"Bearer {access_token}",
    "Content-Type": "application/json",
}

payload = {
    "text": "I am a nurse who takes care of many people.",
    "model": "orpheus-3b-tts",   # default (Optional)
    "voice": "salt_lug_0001",     # catalog tag; see GET /tasks/voice/speakers
    "language": "eng",            # required for orpheus-3b-tts (ISO code or full name)
}

response = requests.post(url, headers=headers, json=payload)
print(response.json())

orpheus-3b-tts: Languages and Voices

Speaker IDs encode both the source corpus (salt_*, waxal_*, slr32_*, slr129_*, bateesa_*) and the language. Languages marked with an em dash are present in the model’s training mix but do not currently expose individual voice IDs in this checkpoint.

Config	Language	Region	Speaker IDs
`ach`	Acholi	Uganda, South Sudan	`salt_ach_0001`, `waxal_ach_0001`, `waxal_ach_0005`, `waxal_ach_0006`, `waxal_ach_0008`
`afr`	Afrikaans	South Africa, Namibia	`slr32_afr_0009`
`eng`	English	(control language)	`salt_eng_0001`, `salt_eng_0002`, `salt_eng_0003`
`ewe`	Ewe	Ghana, Togo	`slr129_ewe_0001`
`ful`	Fulah	West Africa (Sahel)	`waxal_ful_0003`, `waxal_ful_0004`, `waxal_ful_0006`
`hau`	Hausa	Nigeria, Niger, Chad	`waxal_hau_0004`, `waxal_hau_0006`, `waxal_hau_0007`, `waxal_hau_0008`
`ibo`	Igbo	Nigeria	`waxal_ibo_0003`, `waxal_ibo_0005`, `waxal_ibo_0008`
`kik`	Kikuyu	Kenya	`waxal_kik_0003`, `waxal_kik_0004`
`kin`	Kinyarwanda	Rwanda	`bateesa_kin_0001`
`lgg`	Lugbara	Uganda, DRC	—
`lin`	Lingala	DRC, Republic of Congo	`slr129_lin_0001`
`lug`	Luganda	Uganda	`salt_lug_0001`, `waxal_lug_0002`–`waxal_lug_0008`
`luo`	Luo (Dholuo)	Kenya, Tanzania	`waxal_luo_0001`–`waxal_luo_0004`
`nyn`	Runyankole	Uganda	`salt_nyn_0001`, `waxal_nyn_0003`, `waxal_nyn_0004`, `waxal_nyn_0007`, `waxal_nyn_0008`
`sot`	Sesotho	Lesotho, South Africa	—
`swa`	Swahili	East Africa	`waxal_swa_0006`, `waxal_swa_0007`
`teo`	Ateso	Uganda, Kenya	`salt_teo_0001`
`tsn`	Setswana	Botswana, South Africa	—
`xho`	Xhosa	South Africa	`slr32_xho_0012`
`yor`	Yoruba	Nigeria, Benin	`waxal_yor_0002`, `waxal_yor_0006`, `waxal_yor_0008`

Per-language quality scales with the amount of training data collected for that language. Audition the voices before relying on a particular speaker — use the discovery snippet under Listing Voices.

Single Synthesis (spark-tts, fixed voices)

payload = {
    "text": "I am a nurse who takes care of many people.",
    "model": "spark-tts",
    "voice": "luganda_female",   # voice name, or the numeric id as a string e.g. "248"
    "response_mode": "url",       # "url" (default), "stream", or "both"
}
response = requests.post(url, headers=headers, json=payload)
print(response.json())

spark-tts Voices

Voice name	ID	Language	Gender
`acholi_female`	241	Acholi	Female
`ateso_female`	242	Ateso	Female
`runyankore_female`	243	Runyankore	Female
`lugbara_female`	245	Lugbara	Female
`swahili_male`	246	Swahili	Male
`luganda_female`	248	Luganda	Female

Response Modes

response_mode applies to spark-tts on Modal:

url — generate audio, upload to GCP, return a signed URL (valid ~30 minutes) — default
stream — stream raw audio chunks directly
both — stream audio and return a final signed URL

Listing Voices

auth = {"Authorization": f"Bearer {access_token}"}

# Orpheus voices grouped by language (default)
print(requests.get("https://api.sunbird.ai/tasks/voice/speakers", headers=auth).json())

# spark-tts fixed voices
print(requests.get(
    "https://api.sunbird.ai/tasks/voice/speakers",
    headers=auth,
    params={"model": "spark-tts"},
).json())

Batch Synthesis (orpheus-3b-tts)

Synthesize up to 128 items in a single request:

url = "https://api.sunbird.ai/tasks/audio/speech/batch"
payload = {
    "items": [
        {"text": "Good morning.", "voice": "salt_lug_0001"},
        {"text": "How are you?", "voice": "salt_eng_0001"},
    ]
}
response = requests.post(url, headers=headers, json=payload)
print(response.json())

Refreshing an Expired URL

Signed URLs expire after ~30 minutes. Re-sign a stored object with GET /tasks/audio/speech/url:

print(requests.get(
    "https://api.sunbird.ai/tasks/audio/speech/url",
    headers={"Authorization": f"Bearer {access_token}"},
    params={"gcs_object": "orpheus_tts/2026-06-03/abc.wav"},
).json())

Response

{
  "audio_url": "https://storage.googleapis.com/.../tts_audio/....wav?...",
  "model": "orpheus-3b-tts",
  "platform": "modal",
  "voice": "salt_lug_0001",
  "audio_url_expires_at": "2026-06-03T22:59:36.954061Z",
  "language": "lug",
  "sample_rate": 24000,
  "duration_seconds": 4.0,
  "gcs_object": "orpheus_tts/2026-06-03/....wav",
  "request_id": "0f1e2d3c4b5a...",
  "timings_ms": {"inference_ms": 1820.5, "upload_ms": 234.1, "total_ms": 2095.6}
}

The audio_url is a temporary signed URL valid for ~30 minutes. Download or stream the audio promptly, or re-sign it with GET /tasks/audio/speech/url.

Getting Started

Guides

Support

Single Synthesis (orpheus-3b-tts, default)

Parameters

orpheus-3b-tts: Languages and Voices

Single Synthesis (spark-tts, fixed voices)

spark-tts Voices

Response Modes

Listing Voices

Batch Synthesis (orpheus-3b-tts)

Refreshing an Expired URL

Response

​Single Synthesis (orpheus-3b-tts, default)

​Parameters

​orpheus-3b-tts: Languages and Voices

​Single Synthesis (spark-tts, fixed voices)

​spark-tts Voices

​Response Modes

​Listing Voices

​Batch Synthesis (orpheus-3b-tts)

​Refreshing an Expired URL

​Response

Single Synthesis (orpheus-3b-tts, default)

Parameters

orpheus-3b-tts: Languages and Voices

Single Synthesis (spark-tts, fixed voices)

spark-tts Voices

Response Modes

Listing Voices

Batch Synthesis (orpheus-3b-tts)

Refreshing an Expired URL

Response