6 best orchestration tools to build AI voice agents in 2025

AI voice agents turn frustrating IVR trees into actual conversations that get things done. These systems understand natural speech, maintain context throughout interactions, and respond with voices that sound (sometimes indistinguishably) human.

Behind most great voice agents is an orchestration tool that connects the necessary models, including:

1. Speech-to-text (STT) that accurately captures what customers say in real-time
2. Large language models (LLMs) that figure out what they actually want
3. Text-to-speech (TTS) that deliver responses that sound natural

When these pieces work in harmony, customers get the help they need without the friction. In fact, industry projections show 70% of contact centers plan to implement voice AI by the end of 2025.

However, finding the right orchestration platform makes a big difference. Here are the orchestration tools you can trust to deliver results in 2025.

A quick comparison of the top 6 orchestration tools

1. Vapi

Key Features

• No-code Flow Studio
• Multi-language support
• Tool calling capabilities
• A/B testing
• 1500+ integrations
• API-native for granular control

Best For

Developers who need a blend of visual flow design and robust API options for deeper custom logic

AssemblyAI Integration?

Yes

2. LiveKit

Key Features

• Open-source framework
• Multimodal & pipeline agents
• Function calling
• Turn detection for lifelike conversations
• Telephony integration
• Rich plugin ecosystem

Best For

Teams seeking maximum customization and the ability to self-host or deeply extend the platform

AssemblyAI Integration?

Yes

3. Daily/Pipecat

Key Features

• Open-source Python framework
• Vendor-neutral orchestration
• Real-time media transport for voice/video
• Multi-turn context management
• Phrase endpointing
• Multimodal support (audio, text, images, etc.)

Best For

Technical teams needing maximum flexibility in customizing or orchestrating AI services

AssemblyAI Integration?

Yes

4. Retell

Key Features

• Proprietary turn-taking models
• Interruptibility for natural flow
• Multi-language support
• Strong low-latency focus
• Deployable on web, mobile, & telephony

Best For

Businesses requiring highly responsive, natural-sounding voice agents in customer-facing roles

AssemblyAI Integration?

No

5. Synthflow

Key Features

• No-code interface for rapid deployment
• 200+ built-in tool integrations
• Ready-made templates
• Multi-language support
• Enterprise security & compliance features

Best For

Non-technical teams and enterprises requiring quick deployment with minimal coding

AssemblyAI Integration

No

6. Bland

Key Features

• Self-hosted end-to-end infrastructure
• Remarkably human-like voice
• Custom prompts and guardrails
• 24/7 availability
• Enterprise features (analytics, fine-tuning)

Best For

Enterprise customers requiring security, control and human-like interactions

AssemblyAI Integration?

No

What to consider when choosing an orchestration tool

There are must-have factors you’ll need from your orchestration tool. The right choice depends entirely on your specific use case, team capabilities, and business requirements:

• Technical expertise required: Does your team have the engineering resources to work with APIs and build custom integrations, or do you need a no-code solution that business users can manage? Teams almost always underestimate the technical debt created by choosing platforms that exceed their maintenance capabilities.
• Customization depth: How much control do you need over conversation design, error handling, and integration logic? More customizable platforms offer greater flexibility but typically require more development resources to implement and maintain.
• Deployment model: Cloud-based solutions offer quicker setup and lower maintenance, while self-hosted options provide greater security and data control for regulated industries.
• Latency requirements: Does your use case demand fast, real-time responses? Lower latency creates more natural conversations for users.
• Integration capabilities: How easily does the platform connect with your existing systems like CRM, knowledge bases, and telephony infrastructure? Pre-built connectors reduce implementation time.
• Pricing structure: Usage-based models scale with your needs but can become unpredictable, while subscription approaches offer cost certainty. Most platforms now charge based on some combination of conversation minutes, API calls, and feature tiers.
• Scalability: Can the platform handle your projected volume during peak periods without degrading conversation quality? This becomes non-negotiable when advanced AI agents move from pilot to production.

Top 6 orchestration tools for building AI voice agents

1. Vapi: Developer-friendly with visual design options

Vapi bridges the gap between no-code simplicity and developer flexibility. It's specifically built for the voice-agent use case, and has quickly gained traction for teams that need both visual conversation mapping and API-driven customization.

Key capabilities:

• No-code Flow Studio for visual conversation design without coding
• API-native architecture with programmatic access to every feature
• Multi-language support for global deployments
• Tool calling capabilities for integrating external data sources
• A/B testing to optimize conversation performance
• 1500+ integrations with third-party services

Vapi takes a unique dual approach. The visual interface helps business stakeholders map out conversation flows, while developers can access the same functionality through APIs for deeper customization. This flexibility means you can start simple and add complexity as your voice agent evolves.

Vapi natively integrates with AssemblyAI's streaming speech-to-text API to deliver the must-have low-latency transcription for natural-feeling conversations. It's a great solution for customer service applications where cross-channel consistency matters.

2. LiveKit: Open-source with maximum control

LiveKit is a fully open-source platform for building real-time media applications. LiveKit Agents builds on top of this foundation to provide tools for developers to easily build AI agents.

Key capabilities:

• Open-source codebase you can actually modify and extend
• Multimodal support spanning voice, video, and text interactions
• Function calling for triggering complex actions or retrieving data
• Turn detection that makes conversations feel more natural
• Native telephony integration for both inbound and outbound calls
• Rich plugin ecosystem that keeps growing with the community

Since LiveKit is open-source, you won’t get locked in to third-party hosting in perpetuity. And the Agent’s framework flexibility means you can build your agents and systems tailored to your use-case.  Need a specific feature? Build it. Want to customize how components interact? You can.

AssemblyAI's streaming model plugin for LiveKit Agents makes it easy to convert speech-to-text in real-time. Several enterprise customers have built distinctive voice experiences they couldn't create on other platforms.

3. Daily/Pipecat: Flexible open-source orchestration

The team at Daily built Pipecat because they couldn't find an orchestration framework flexible enough for their own needs. This open-source Python framework doesn't lock you into specific vendors or approaches—instead, it offers a wide set of composable tools so developers can build how and with what they want.

Key capabilities:

• Vendor-neutral design that works with any AI services
• Multi-turn context management for coherent conversations
• Real-time media transport optimized for voice and video
• Phrase endpointing that catches natural speaking breaks
• Multimodal support for richer interaction models
• Completely customizable conversation workflows

Pipecat is all about flexibility. Most platforms push you toward their preferred AI providers, but Pipecat lets you mix and match components based on performance, cost, and specific requirements. Need to swap out an LLM or try a different text-to-speech engine? No problem.

The framework integrates cleanly with AssemblyAI's streaming speech-to-text model while allowing developers to control exactly how speech recognition fits into their architecture.

4. Retell: Best for natural conversation

Retell zeroes in on the biggest challenge in voice technology: making interactions feel natural. It focuses on eliminating the awkward pauses and robotic exchanges that unhinge most voice systems.

Key capabilities:

• Proprietary turn-taking models that mimic human conversation patterns
• Interruptibility so callers can cut in without the system breaking
• Industry-leading low latency (responses typically under 500ms)
• Multi-language support right out of the box
• Deployment options for web, mobile, and telephony
• Adaptive error recovery when conversations go off track

While other platforms treat voice as just another channel, Retell optimizes every component around creating natural dialogue flow. The system actually listens for interruptions and adapts in real-time (just like humans do).

5. Synthflow: No-code for faster deployment

Synthflow strips away the complexity of voice agent development. It's built for business teams who need functional voice agents without diving into code or managing infrastructure.

Key capabilities:

• Complete no-code interface with drag-and-drop simplicity
• 200+ pre-built integrations that work out of the box
• Ready-made templates for common business scenarios
• Multi-language capabilities with minimal configuration
• Enterprise security features for regulated industries
• Usage-based pricing that scales with your needs

Synthflow focuses on accessibility. Other platforms require at least some development resources, but Synthflow puts voice agent creation in the hands of business users. The template library covers everything from appointment scheduling to customer surveys to let you customize existing flows rather than starting from zero.

Synthflow offers SMBs and departments with limited IT support the fastest path from concept to deployment.

6. Bland: Self-hosted security for enterprise

Bland solves the security concerns that keep voice agents out of highly-regulated industries. This enterprise-focused platform provides complete infrastructure control without sacrificing conversation quality or features.

Key capabilities:

• Self-hosted end-to-end infrastructure that never leaves your network
• Human-like voice quality that maintains brand consistency
• Custom prompts and guardrails to enforce business rules
• 24/7 availability with built-in redundancy
• Analytics dashboard for measuring performance and ROI
• Warm transfer capabilities when human intervention is needed

Voice interactions contain sensitive customer information that many organizations can't legally process in the cloud. Bland keeps everything on your infrastructure: transcription, processing, and response generation all happen behind your firewall.

Financial services, healthcare, and government agencies have been quick to adopt Bland due to its enterprise-grade security.

AssemblyAI's role in the voice agent ecosystem

Voice agents are only as good as their ability to understand what people are saying. That's where AssemblyAI's specialized speech-to-text functionality creates a foundation for natural, responsive interactions.

AssemblyAI’s streaming API is built for voice agent applications:

• Ultra-low latency that enables fast response times to eliminate the awkward pauses that make conversations feel robotic.
• Intelligent endpointing (turn detection) that accurately detects when someone has finished speaking, even with natural pauses and hesitations.
• High accuracy for proper nouns and domain-specific terminology to correctly capture the names, brands, and technical terms that matter to your business.

We've also designed our speech-to-text technology with flexible deployment options.

Find the right tool for your voice strategy

Choosing the right orchestration platform comes down to your requirements and technical resources. There’s no one-size-fits-all tool, but you’ll find an orchestration solution that fits your needs here:

• For teams balancing speed and flexibility, Vapi offers visual design with API escape hatches
• When maximum customization matters, LiveKit and Pipecat provide open-source foundations with lots of control for developers
• If conversation quality is your priority, Retell's focus on turn-taking creates natural interactions
• When you need rapid deployment without coding, Synthflow delivers results quickly
• For strict security requirements, Bland's self-hosted approach keeps sensitive data under your control

What matters most is building on a foundation that can grow with your needs and adapt to changing technology.

AssemblyAI is pushing speech recognition forward with regular model updates that improve accuracy, reduce latency, and improve the voice experience. Start building your voice agent today with free API credits and see what's possible when you combine powerful orchestration with industry-leading speech recognition.