Select a voice or call the documented feature route; no separate model_id is exposed.
Access
GET/POST /v1/synthesize; choose the voice query parameter from the catalog.
Regions
Use the service-instance URL for the provisioned region. Product-edition and voice-specific availability apply; no universal residency guarantee inferred.
voiceSelectors
en-AU_HeidiExpressive, en-AU_JackExpressive, en-US_AllisonExpressive, en-US_EmmaExpressive, en-US_LisaExpressive, en-US_MichaelExpressive, en-GB_GeorgeExpressive, pt-BR_LucasExpressive, es-LA_DanielaExpressiveSource for voiceSelectors (opens in a new tab)
Prices retain their published currencies and billing units below.
Published billing units · original currency · observed 14 Oct 2026
Category
Usage
Rate
Unit
Starting TTS service price
Standard synthesis, starting at1
$0.02
1,000 characters
Rate conditions
Published service-level starting rate, not a separately verified fixed rate for each voice. Whitespace excluded from billing. Lite/Premium/custom-voice and self-hosted plans have separate terms.
Select a voice or call the documented feature route; no separate model_id is exposed.
Access
WebSocket /v1/synthesize; choose voice in the connection URL. One text request is synthesized before the service closes the connection.
Regions
Use the service-instance URL for the provisioned region. Product-edition and voice-specific availability apply; no universal residency guarantee inferred.
voiceSelectors
en-AU_HeidiExpressive, en-AU_JackExpressive, en-US_AllisonExpressive, en-US_EmmaExpressive, en-US_LisaExpressive, en-US_MichaelExpressive, en-GB_GeorgeExpressive, pt-BR_LucasExpressive, es-LA_DanielaExpressiveSource for voiceSelectors (opens in a new tab)
Prices retain their published currencies and billing units below.
Published billing units · original currency · observed 14 Oct 2026
Category
Usage
Rate
Unit
Starting TTS service price
Standard synthesis, starting at1
$0.02
1,000 characters
Rate conditions
Published service-level starting rate, not a separately verified fixed rate for each voice. Whitespace excluded from billing. Lite/Premium/custom-voice and self-hosted plans have separate terms.
Retention, training use, regional processing and enterprise terms have not been summarized for this endpoint.
Caching
Caching can reuse earlier input processing. Availability, lifetime and billing depend on the endpoint. A cache hit still generates a new response.
01 / INITIAL INPUTProcess & retain
The system processes eligible input and retains reusable state.
02 / LATER REQUESTCheck available state
Reuse depends on matching input, session state and the cache policy.
03 / CACHE HITReuse & generate
Reusing state can reduce repeated work. Any charges follow the billing rules below.
IBM Watson Text to Speech
Not verified
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
How it works
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Minimum reusable input
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Lifetime & refresh
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
How to enable it
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Usage fields
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Billing rules
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Limits & data boundaries
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
No verified cache rate for this endpoint. An empty rate is not a zero charge.
IBM Watson Text to Speech
Not verified
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
How it works
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Minimum reusable input
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Lifetime & refresh
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
How to enable it
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Usage fields
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Billing rules
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
Limits & data boundaries
Not collected
No provider-priced inference cache contract verified. Client-side audio reuse is not provider prompt caching.
No verified cache rate for this endpoint. An empty rate is not a zero charge.
Voice choices
9 voices
Choose a voice within Watson Text to Speech: Expressive Neural. These are API voice identifiers, not additional model releases. Source links document each voice.
No benchmark observations have been added for this model. We do not turn a vendor description into a performance score.
Latency and throughput depend on the host, request size, reasoning settings and load. There is no measured speed or global usage figure in this record.
The record behind the model
Why it is included
IBM documents this proprietary Watson speech service model or managed voice family. The service exposes recognition/voice selectors, not downloadable trained checkpoints. Closed-weight classification is inferred for the product model; public Granite Speech research releases and referenced open research implementations are separate.
