Controlling volume, speaking rate, and pitch

<prosody>

Prosody tag attributes are fully supported by the standard TTS voices. Neural and long-form voices support the volume and rate attributes, but don't support the pitch attribute.

To control the volume, rate, or pitch of your selected voice, use the prosody tag.

Volume, speech rate, and pitch are dependent on the specific voice selected. In addition to differences between voices for different languages, there are differences between individual voices speaking the same language. Because of this, while attributes are similar across all languages, there are clear variations from language to language and no absolute value is available.

The prosody tag has three attributes, each of which has several available values to set the attribute. Each attribute uses the same syntax:

<prosody attribute="value"></prosody>

• volume

  • default: Resets volume to the default level for the current voice.

  • silent, x-soft, soft, medium, loud, x-loud: Sets the volume to a predefined value for the current voice.

  • +ndB, -ndB: Changes volume relative to the current level. A value of +0dB means no change, +6dB means approximately twice the current volume, and -6dB means approximately half the current volume.

  For example, you could set the volume for a passage as follows:

  <speak>
       Sometimes it can be useful to <prosody volume="loud">increase the volume 
       for a specific speech.</prosody>                     
  </speak>

  Or you could set it this way:

  <speak>
       And sometimes a lower volume <prosody volume="-6dB">is a more effective way of 
       interacting with your audience.</prosody>  
  </speak>

• rate

  • x-slow, slow, medium, fast,x-fast. Sets the pitch to a predefined value for the selected voice.

  • n%: A non-negative percentage change in the speaking rate. For example, a value of 100% means no change in speaking rate, a value of 200% means a speaking rate twice the default rate, and a value of 50% means a speaking rate of half the default rate. This value has a range of 20-200%.

  For example, you could set the speech rate for a passage as follows:

  <speak>
       For dramatic purposes, you might wish to <prosody rate="slow">slow up the speaking 
       rate of your text.</prosody>                     
  </speak>

  Or you could set it this way:

  <speak>
       Although in some cases, it might help your audience to <prosody rate="85%">slow 
       the speaking rate slightly to aid in comprehension.</prosody>  
  </speak>

• pitch

  • default: Resets pitch to the default level for the current voice.

  • x-low, low, medium, high, x-high: Sets the pitch to a predefined value for the current voice.

  • +n% or -n%: Adjusts pitch by a relative percentage. For example, a value of +0% means no baseline pitch change, +5% gives a little higher baseline pitch, and -5% results in a little lower baseline pitch.

  For example, you could set the pitch for a passage as follows:

  <speak>
       Do you like sythesized speech <prosody pitch="high">with a pitch that is higher 
       than normal?</prosody>                     
  </speak>

  Or you could set it this way:

  <speak>
       Or do you prefer your speech <prosody pitch="-10%">with a somewhat lower pitch?</prosody>  
  </speak>

The <prosody> tag must contain at least one attribute, but can include more within the same tag.

<speak>
     Each morning when I wake up, <prosody volume="loud" rate="x-slow">I speak  
     quite slowly and deliberately until I have my coffee.</prosody>
</speak>

It can also be combined with nested tags, as follows:

<speak>
     <prosody rate="85%">Sometimes combining attributes <prosody pitch="-10%">can 
     change the impression your audience has of a voice</prosody> as well.</prosody>                  
</speak>