Voice Selection

Every agent needs a voice. The voice determines how your agent sounds during calls — its tone, accent, speaking speed, and overall character. Choosing the right voice is important for creating a natural, trustworthy caller experience.

How Voices Work

Voices are provided by your voice provider (Retell AI, Vapi, or Bland.ai). Each provider has its own catalog of available voices, and the selection interface varies depending on which provider powers your agent.

You select a voice when creating an agent and can change it anytime from the Agent Editor.

Voice Selection by Provider

Retell AI

Retell provides a curated library of voices directly in your account.

How to select:

1. Open the agent creation form or agent editor.
2. Under Voice, click the dropdown.
3. Browse the list of available voices. Each shows the voice name.
4. Click the play button to preview a voice.
5. Select the voice you want.

Retell voices are fetched from your Retell account and cached in BuildVoiceAI. If you add custom voices in Retell’s dashboard, click Refresh Voices in BuildVoiceAI to sync the new options.

Vapi

Vapi supports multiple underlying voice engine providers, giving you the widest selection of voice technologies.

How to select:

1. Open the agent creation form or agent editor.
2. Under Voice, first select the Voice Provider — the engine that generates the voice:
   • OpenAI — OpenAI’s text-to-speech voices
   • ElevenLabs — Premium, highly realistic voices
   • PlayHT — Natural-sounding cloned and stock voices
   • Deepgram — Fast, low-latency voices
   • Azure — Microsoft Azure neural voices
   • LMNT — Lightweight, fast voice synthesis
   • Rime AI — AI-generated natural voices
3. Enter the Voice ID for your chosen voice. You can find voice IDs in the respective provider’s documentation or dashboard.

Bland.ai

Bland provides its own voice catalog accessible through their API.

How to select:

1. Open the agent creation form or agent editor.
2. Under Voice, click the dropdown.
3. Browse the list of available Bland voices.
4. Click the play button to preview.
5. Select your preferred voice.

Like Retell, Bland voices are synced from your account. Use Refresh Voices to pull in any new additions.

Custom Voice IDs

All three providers support custom or cloned voices. If you’ve created a custom voice through your provider’s dashboard or API, you can use it in BuildVoiceAI by entering its voice ID directly.

For Retell and Bland, custom voices appear automatically in the dropdown after syncing. For Vapi, enter the custom voice ID in the Voice ID field after selecting the appropriate engine.

Tips for Choosing the Right Voice

Match the voice to the role

• Customer service / receptionist — Choose a warm, friendly voice with a natural conversational tone.
• Sales / lead qualification — Pick a confident, clear voice that conveys enthusiasm.
• Technical support — Use a calm, patient voice that sounds knowledgeable.
• After-hours answering — A professional, reassuring voice works best.

Consider your audience

• B2B callers expect a more professional, neutral tone.
• B2C callers often respond better to a warm, approachable voice.
• Multilingual audiences — Some providers offer voices in multiple languages and accents. Match the voice to the primary language of your callers.

Test with real conversations

The best way to evaluate a voice is to make test calls. A voice that sounds good in isolation may not work as well in a full conversation. Pay attention to:

• How natural it sounds at conversational pace
• How it handles pauses and turn-taking
• Whether it pronounces industry-specific terms correctly
• How it sounds when interrupted mid-sentence

Changing Voices

You can change an agent’s voice at any time from the Agent Editor. The change takes effect on the next call — any call in progress continues with the previous voice.

Changing voices does not affect call history. Past recordings retain the original voice they were made with.