Speech to TextAbout HeartMuLa Transcribe
HeartMuLa Transcribe extracts sung lyrics from an audio file and returns them as text. One audio field, no options, multilingual, billed per transcription rather than per minute.
Call it with the model name heartmula/transcribe/speech-to-text on POST /jobs/createTask, from 8 credits per run ($0.08). New accounts get 30 free credits to try it in the Playground first.
Introduction
It transcribes the sung lyrics in an audio file and returns them as text on the task. It is tuned for vocals over music rather than for plain speech.
HeartMuLa Transcribe extracts sung lyrics from an audio file and returns them as text.
Key features
Tuned for the part general speech models lose
A sung line arrives compressed, doubled, drenched in reverb and competing with instruments in its own frequency range. That is the case a general speech model was never trained on, and where it tends to hand back fragments. This one is tuned for exactly that. The trade runs both ways: for an interview or a podcast, with no mix to fight, a general speech-to-text model is the better tool.
Text on the task, no asset to fetch
No file is written for you to fetch. Read the text off the finished task and send it straight to wherever your lyrics already live.
A back catalog is a multiplication, a clip pile is not
That makes a backlog easy to budget — track count times one number — while a folder of short fragments is the relatively expensive shape.
Request parameters
| Parameter | Required | Description |
|---|---|---|
audio_url | Yes | The voice or music track to use. |
Pricing
Prices are in credits, the same credits you use on the website (1 credit = $0.01). The hold is taken when the task is accepted and settled to the actual charge when it finishes; failed tasks are refunded.
| Option | Credits per run | ≈ USD |
|---|---|---|
| Standard | 7.5 | $0.075 |
Each task is rounded up to whole credits, so one run at the lowest tier costs 8 credits per run ($0.08).
For an exact number before you run, send the same body to POST /jobs/quote.
Use cases
Turn speech into usable text
It transcribes the sung lyrics in an audio file and returns them as text on the task. It is tuned for vocals over music rather than for plain speech. Use this mode to transcribe an audio or video source. Provide a clear recording where possible, then review names, timestamps and any passages with low confidence.
Music catalog metadata
Generate lyric text across a catalog to improve search, display and tagging.
Subtitles for music-backed video
Pull the sung lines out of a track so they can be timed into captions for short-form video, where the vocal sits over a dense mix.
Prompt guide & pro tips
Send a direct URL to the audio file
The field takes a URL, not an upload body. It should point at the audio itself — a stream page or a share link that returns HTML will fail as an invalid asset, not as a bad transcription.
Expect text on the task, not a file
The transcript is returned as text on the task result.
Check the result before iterating
One audio URL in, lyric text out, nothing to configure: no language hint, no timestamps, no speaker labels, no confidence values and no choice of output shape. The model is tuned for sung vocals over music; heavily layered mixes, whispered or screamed vocals and very low-bitrate sources degrade the result, and instrumental audio returns little or nothing. The URL must resolve directly to an audio file — a page that returns HTML fails as an invalid asset.
API quick start
Call the HeartMuLa Transcribe API in three steps
- Create an API key. Sign in to PopNow and create a key in the API console. Keys start with sk-popnow- and use the same credits as the website.
- Send the request. POST /jobs/createTask with model heartmula/transcribe/speech-to-text and an input object that follows the parameter table. The response returns a task ID straight away.
- Get the result. Poll GET /jobs/recordInfo with the task ID, or pass a callBackUrl and we post the result to it. Download the output links when the task succeeds.
# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
-H "Authorization: Bearer $POPNOW_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: $IDEMPOTENCY_KEY" \
-d '{
"model": "heartmula/transcribe/speech-to-text",
"input": {
"audio_url": "https://media.popnow.ai/shortfilm/voices/Aoede-46e4c427.mp3"
}
}'
# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
-H "Authorization: Bearer $POPNOW_API_KEY"Replace the prompt and any links with your own. The API tab has the response, polling and callback reference.
HeartMuLa Transcribe API questions
How much does the HeartMuLa Transcribe API cost?
HeartMuLa Transcribe costs 8 credits ($0.08) per run. Credits are the same as on the website (1 credit = $0.01), new accounts get 30 free credits, and failed tasks are refunded.
What is the model name for HeartMuLa Transcribe in the API?
Put heartmula/transcribe/speech-to-text for Speech to Text in the model field of POST /jobs/createTask.
Can I get timestamps or per-line timing?
No. The output is the lyric text with no timings, no confidence values and no speaker or section labels. Captioning workflows still need their own alignment pass.
Do I have to say which language the audio is in?
No, and you cannot. The model handles multiple languages on its own and does not report which one it detected.
How well does it do on speech rather than singing?
It is tuned for sung lyrics over music. Plain speech will usually transcribe, but a general speech-to-text model is the better tool for interviews, podcasts and meetings.
Can I try HeartMuLa Transcribe without writing code?
Yes. The Playground runs HeartMuLa Transcribe on your PopNow credits, needs no API key, and shows the matching code for every run.