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MOSS-TTS Prompt Fields Guide

Overview

MOSS-TTS exposes official whole-segment prompt fields through the ⚙️ MOSS-TTS Engine node.

These are not Step Audio EditX effects and they are not positional insertions. They are passed to the official MOSS prompt structure for the entire generated segment.

Supported official fields:

  • instruction
  • quality
  • sound_event
  • ambient_sound
  • language
  • duration_tokens

Stability Note

ambient_sound should currently be treated as experimental on base MOSS-TTS inside this suite.

Reason:

  • the official prompt schema exposes ambient_sound
  • but the clearest public OpenMOSS example we found is in the MOSS-SoundEffect documentation path, not as a validated short-utterance base-TTS control

So on MOSS-TTS you may get:

  • weak or missing ambience
  • longer-than-expected generation
  • unstable tails if the model is pushed to the token cap

Important Limitation

MOSS does not treat these like exact inline insertions inside the sentence.

For example:

[Alice|sound_event:Laughter] Hello there.

That means the whole segment is conditioned with the event. It is not positional the way Step Audio EditX paralinguistic tags are.

Engine Fields

You can set official fields directly on the engine node:

  • instruction: whole-segment speaking instruction
  • quality: whole-segment quality/style hint
  • sound_event: whole-segment event hint such as Laughter, Sigh, Breathing
  • ambient_sound: whole-segment ambience hint such as Rain, Crowd, Forest

These apply to every generated segment that uses that engine config.

Per-Segment Override Syntax

For per-segment overrides, use [] parameter switching.

Supported forms:

[Narrator|instruction:Speak softly and calmly] Hello there.
[Narrator|quality:Studio recording] Hello there.
[Narrator|sound_event:Laughter] Hello there.
[Narrator|ambient_sound:Rain on window] Hello there.

Inside normal character tags, combine them like this:

[Alice|instruction:Speak softly and calmly] Hello there.
[Bob|quality:Telephone call quality|ambient_sound:Office room tone] Hi.
[Alice|sound_event:Laughter] That's funny.

These are whole-segment overrides, not exact insertion points.

Why Not <>

MOSS does not have true native inline positioning for these controls.

So <> should stay free for real inline post-processing tags such as Step Audio EditX effects. Using <> for MOSS prompt fields would blur two different systems and create confusion.

Examples

Direct engine fields

Set on the engine node:

  • sound_event = Laughter
  • quality = Studio recording

Text:

[Alice] Hello there!

Result: the entire Alice segment is conditioned with Laughter and Studio recording.

Per-segment [] syntax

[Alice|sound_event:Laughter] Hello there!
[Bob|ambient_sound:Rain] Nice to meet you.

Result:

  • Alice segment uses sound_event = Laughter
  • Bob segment uses ambient_sound = Rain

Conflicts and Precedence

  • If you set an engine field and also override it in [], the [] value wins for that segment.
  • These MOSS prompt fields are not supposed to use <>.

Native TTSD Dialogue Note

MOSS-TTSD-v1.0 generates one native dialogue request across the formatted [S1]...[S5] conversation.

So these official fields still apply to the whole TTSD request, not to one precise speaker turn inside that request.

Native TTSD Compatibility Rules

Native TTSD mode is strict in this suite.

If any of these are detected, generation fails with an explicit error instead of auto-switching models:

  • pause tags
  • inline Step Audio EditX tags
  • per-segment [] parameter changes
  • more than 5 speakers

This applies to both normal TTS Text and SRT workflows.

Required action when that happens:

  • switch to Custom Character Switching
  • choose a standard MOSS model (MOSS-TTS-Local-Transformer or MOSS-TTS)

When To Use Something Else

If you need exact placement of laughter/breathing/cough inside the sentence, use:

  • Step Audio EditX inline tags and audio editor workflow
  • an engine with true native positional tag support, such as CosyVoice3

Use MOSS prompt fields when you want official MOSS conditioning, not precise insertion control.

If you specifically want generated environmental audio like rain, traffic, or scene beds, MOSS-SoundEffect is the more correct OpenMOSS model family target than base MOSS-TTS.