Acting Instructions Guide

Octave supports supplying acting instructions to guide aspects of speech delivery:

• Emotional tone: happiness, sadness, excitement, nervousness, etc.
• Delivery style: whispering, shouting, rushed speaking, measured pace, etc.
• Performance context: speaking to a crowd, intimate conversation, etc.
• Speaking rate: the rate at which the speech is delivered, faster or slower.
• Trailing silence: injecting pauses in the speech for a specified duration in seconds.

In the following section, we’ll explore the ways in which you can provide acting instructions to Octave through the API.

Providing acting instructions

The TTS API offers parameters which allow you to control how an individual utterance is performed. These parameters can be used individually or combined for precise control over speech output:

• description: provide acting instructions in natural language.
• speed: adjust the relative speaking rate on a non-linear scale from 0.5 (much slower) to 2.0 (much faster), where 1.0 represents normal speaking pace. Note that changes are not proportional to the value provided - for example, setting speed to 2.0 will make speech faster but not exactly twice as fast as the default.
• trailing_silence: specify a duration of trailing silence (in seconds) to add to an utterance.

In this section we’ll leverage acting instructions to guide Octave’s speech output for guided meditation.

Before we apply acting instructions, let’s first take a look at a request that does not contain any acting instructions:

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curl "https://api.hume.ai/v0/tts/stream/json" \
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  -H "X-Hume-Api-Key: $HUME_API_KEY" \
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  --json '{
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    "utterances": [
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      {
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        "text": "Let us begin by taking a deep breath in.",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        }
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      },
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      { 
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        "text": "Now, slowly exhale.",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        }
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      }
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    ]
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  }'

In the following steps, we’ll iteratively improve Octave’s delivery by specifying different types of acting instructions to better simulate guided meditation.

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curl "https://api.hume.ai/v0/tts/stream/json" \
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  -H "X-Hume-Api-Key: $HUME_API_KEY" \
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  --json '{
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    "utterances": [
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      {
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        "text": "Let us begin by taking a deep breath in.",
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        "description": "calm, pedagogical",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        }
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      },
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      { 
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        "text": "Now, slowly exhale.",
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        "description": "calm, serene",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        }
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      }
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    ]
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  }'

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curl "https://api.hume.ai/v0/tts/stream/json" \
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  -H "X-Hume-Api-Key: $HUME_API_KEY" \
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  --json '{
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    "utterances": [
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      {
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        "text": "Let us begin by taking a deep breath in.",
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        "description": "calm, pedagogical",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        },
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        "speed": 0.65
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      },
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      { 
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        "text": "Now, slowly exhale.",
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        "description": "calm, serene",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        },
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        "speed": 0.65
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      }
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    ]
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  }'

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curl "https://api.hume.ai/v0/tts" \
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  -H "X-Hume-Api-Key: $HUME_API_KEY" \
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  --json '{
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    "utterances": [
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      {
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        "text": "Let us begin by taking a deep breath in.",
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        "description": "calm, pedagogical",
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        "voice": {
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          "name": "Ava Song",
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          "provider": "HUME_AI"
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        },
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        "speed": 0.65,
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        "trailing_silence": 4
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      },
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      { 
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        "text": "Now, slowly exhale.",
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        "description": "calm, serene",
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        "speed": 0.65
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      }
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    ]
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  }'

Combine natural language descriptions, speed adjustments, and pauses to control Octave’s delivery. In the meditation example, these settings turn a simple line into naturally paced speech. Tune these controls together to match your intended delivery.

Best practices

• Keep it concise: Short instructions work best—aim for no more than 100 characters. Instead of long phrases like “The speaker is scared and in a hurry to leave”, write “frightened, rushed”.
• Use precise emotions: Instead of broad terms like “sad”, use specific emotions like “melancholy” or “frustrated”.
• Combine for nuance: Pair emotions with delivery styles, e.g., “excited but whispering” or “confident, professional tone”.
• Indicate pacing: Use terms like “rushed”, “measured”, “deliberate pause” to adjust speech rhythm.
• Specify the audience: Instructions like “speaking to a child” or “addressing a large crowd” help shape delivery.
• Use speed for adjusting speech rate: Rather than using the description field to instruct slower or faster speech, leverage the speed parameter.

Examples

The table below demonstrates how acting instructions can transform the same text into different delivery styles: