Emotion & tone

Overview

Soniox Text-to-Speech lets you control how the words are delivered, not just which words are spoken. You have two toolkits, and they combine freely:

Audio tags — bracketed cues like [excited], [whispering], or [laughs] that control emotion, tone, human sounds, and delivery.
Text formatting & punctuation — capitalization, emphasis, elongation, and punctuation marks written into the words themselves (UPPERCASE, *stress*, sooo, ..., —, ?!).

Both are written directly into the text you send via API:

{
  "model": "tts-rt-v2",
  "language": "en",
  "voice": "Adrian",
  "audio_format": "wav",
  "text": "[excited] INCREDIBLE news! [calm] Let me explain what happened."
}

These controls shape the expressive layer: emotion, sounds, emphasis, and local pacing. To change the overall speaking rate use the speed parameter instead.

Audio tags

Place a bracketed tag before the text you want to affect to set how it is delivered. The tag describes the feeling or manner; the words after it inherit that delivery.

The tags listed below are not exhaustive. Other tags may also work — test them before relying on them in production.

Always write audio tags in English, regardless of the text language. Localized tags (for example, [emocionado] instead of [excited]) are not supported.

[excited] ¡Tengo noticias INCREÍBLES! [calm] Déjame explicarte lo que pasó.

Emotion & tone

Category	Tags
Emotion	`[happy]` `[sad]` `[angry]` `[excited]` `[nervous]` `[fearful]` `[surprised]` `[annoyed]` `[relieved]` `[disappointed]` `[curious]` `[delighted]` `[calm]`
Tone & manner	`[warm]` `[stern]` `[serious]` `[playful]` `[sarcastic]` `[flirty]` `[deadpan]` `[sincerely]` `[reassuringly]` `[dramatically]` `[mockingly]`

[excited] INCREDIBLE news! [calm] Let me explain what happened.
[sad] I don't know what to say anymore.
[warm] [softly] Hey. [reassuringly] It's okay.

Human sounds

Non-lexical actions you can't spell as a word go in brackets:

Category	Tags
Amusement	`[laughs]` `[chuckles]` `[giggles]`
Sadness	`[sobs]` `[sniffles]` `[whimpers]`
Relief / exasperation	`[sighs]` `[exhales]`
Surprise	`[gasps]`
Effort / pain	`[grunts]` `[groans]`
Physiological	`[clears throat]` `[coughs]` `[yawns]`

[chuckles] And I just let go — [laughs] best thing all week.
[sighs] I really thought I'd get the job. [sniffles] Oh well.

Spoken interjections like Hmm, Um, or Mhm are different: write them as ordinary words, not tags — see Spoken interjections.

Sound effects related to the environment ([dog barks], [phone rings]) are not supported.

Volume, pace & pitch

Tags that control the mechanics of delivery: how loud, how fast, and at what pitch.

Category	Tags
Volume	`[whispering]` `[softly]` `[loudly]` `[shouting]` `[getting louder]` `[getting quieter]` `[trailing off]` `[muttering]`
Pace & rhythm	`[slowly]` `[quickly]` `[rushed]` `[drawn out]` `[hesitantly]`
Pitch	`[high-pitched]` `[low voice]` `[monotone]`
Voice quality	`[breathy]` `[raspy]` `[trembling voice]` `[shaky]`

[whispering] Something's out there. [slowly] Do not move.
[shouting] Get out of there!
[low voice] Sit. [hesitantly] We need to talk.

Pauses

Use tags to insert deliberate silence:

[pause] — the default pause; use it for most cases.
[long pause] — a longer, more dramatic gap; use occasionally.

For shorter beats inside a sentence, use punctuation (..., ,) instead.

So, here's the plan. [pause] Let me walk you through it.

Tag limitations

Tags work best when they stay close to the short, single-purpose forms listed above.

Keep each tag simple. [laughs] and [shouting] are reliable; compound directions like [laughs and screams really loud] or [says the next line sarcastically] are not. Rewrite the intent into the words themselves.
Stack sparingly. Two tags before a clause ([warm] [softly]) normally combine well. Five stacked tags pull in different directions and will not produce a good result.
Unrecognized tags may be spoken. If the model doesn't interpret a tag as direction, it can read the bracketed words aloud. Test any tag outside the tables above before shipping it.
The voice has to support the direction. A soft, narrative voice asked for [shouting] will only go so far. Pick a voice whose range matches the scene instead of forcing it with tags.

You can shape delivery without any tags, just by how you write the words. These conventions are language-agnostic and stack with audio tags — for example, [sad] *please* don't go... combines an emotion tag, an emphasized word, and a trailing pause.

Formatting

Convention	Effect
`UPPERCASE`	Loud / shouting / strong emphasis
`stress`	Stress this word (pitch + emphasis)
`sooo`, `noooo`, `waaait`	Vowel elongation - drawl, sarcasm, whining
`I-I-I don't...`	Stutter / stammer
`lowercase everything`	Flat / muted / deadpan

Punctuation

Convention	Effect
`...`	Pause / trailing off / hesitation
`—` / `--`	Abrupt cut-off / self-interruption
`,`	Short pause / breath
`!` / `!!!`	Rising excitement / intensity
`?` / `???`	Question / disbelief
`?!`	Incredulous / startled

You did WHAT?!
Oh, *you* noticed the haircut?
Wait... N-n-no. That can't be right.

Keep these conventions close to how people actually write. A few repeated characters read as intent (waaait, !!!, N-n-no); dozens of them (whaaaaaaaaaaaaaaaaait, !!!!!!!!!!) will degrade delivery. The same goes for stacking everything at once — SOOOO *AMAZING*!!!??? is more likely to sound off than emphatic.

Spoken interjections

Interjections the voice should actually say are written as ordinary words. Do not put these in tags.

Sound	Conveys
`Hmm`, `Hm`	Thinking
`Um`, `Uh`	Hesitation / fillers
`Mhm`, `Uh-huh`	Agreement
`Ugh`, `Eww`	Disgust
`Oof`, `Ow`, `Ouch`	Pain
`Mmm`	Pleasure / satisfaction
`Phew`	Relief

[clears throat] Hey, it's me. Got a sec? Mhm.

Putting it together

The real power comes from layering both toolkits together. Below are three examples with fully annotated input. Pick a voice whose character matches the scene and try in our playground.

[whispering] Shh, shh — she's coming. [excited] SURPRISE!!! [loudly] Happy birthday!!! 
[laughing] Look at her FACE! [happy] Oh, this is the best.

[yawning] Okay... [drawn out] iiit's so late. [tired] [sighing] What a day. 
[muttering] just five more minutes... [softly] g'night.

[excited] Okay okay open it, open it! 
[gasp] [awe] No way — is this the — [voice cracking] [happy] oh my gosh, I can't believe you remembered! 
[sobs] [laughing] I'm crying, I'm actually crying.

Audio tags don't override the text. They work together with it. The model reads the tag in the context of the words that follow, so [excited] on a flat sentence sounds forced, while [excited] SURPRISE!!! sounds natural. Write the words with the emotion already in them, then use a few well-placed tags to lead the clause and let punctuation and formatting carry the rest.

Emotion & tone

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