Audiobook workflows benefit from repeatable naming, stable voice settings, and chapter-level files. The CLI gives an agent a simple command surface for generating drafts, rerendering chapters, and keeping approved audio separate.
Prepare defaults
Set the voice and model once before generating chapters:
cast config set voice-id tc_xxx
cast config set model ssfm-v30
cast config set format mp3
If you need a project-specific voice, clone it first and store the returned uc_ voice ID:
cast voices clone narrator-sample.wav --name "Narrator Draft"
cast config set voice-id uc_xxx
Generate chapters
cast "$(cat chapter-01.txt)" \
--emotion smart \
--out audiobook/chapter-01.mp3 \
--format mp3
cast "$(cat chapter-02.txt)" \
--emotion smart \
--out audiobook/chapter-02.mp3 \
--format mp3
Generate captions or review timing
cast "$(cat chapter-01.txt)" \
--emotion smart \
--out audiobook/chapter-01.wav \
--timestamps-out audiobook/chapter-01.timestamps.json
Use JSON for detailed review timing, or write .srt / .vtt when the audiobook content also needs a video preview.
Use emotion for scene changes
For short passages with a known tone, preset emotion can be more controllable than smart emotion:
cast "The room fell silent as the letter slipped from her hand." \
--emotion preset \
--emotion-preset sad \
--emotion-intensity 1.2 \
--out audiobook/scene-letter.mp3
For passages where surrounding context matters, pass neighboring text:
cast "She opened the door and froze." \
--emotion smart \
--prev-text "The hallway had been empty a moment ago." \
--next-text "A familiar voice whispered her name." \
--out audiobook/scene-door.mp3
Agent prompt pattern
Generate audiobook draft files from the chapter text files.
Use the same voice for every chapter.
Write output to ./audiobook.
Use one MP3 per chapter.
For chapters that also need video previews, generate an SRT file next to the audio.
If a chapter fails, report the filename and keep going.
File naming
| Asset | Suggested filename |
|---|---|
| Full chapter | chapter-01.mp3 |
| Scene revision | chapter-01-scene-03-v2.mp3 |
| Approved final | chapter-01-final.mp3 |
| Alternate delivery | chapter-01-alt-happy.mp3 |
When to use advanced features
| Need | Recommended feature |
|---|---|
| Consistent narrator identity | cast config set voice-id ... |
| Temporary narrator matching a sample | cast voices clone narrator-sample.wav --name "Narrator Draft" |
| Chapter review timing | --timestamps-out chapter-01.timestamps.json |
| Video preview for a chapter | --timestamps-out chapter-01.srt |
| Quick approval playback | cast "one review sentence" without --out |