Tortoise TTS

Ultra

Ultra-High Quality Speech with Unmatched Naturalness

Very Slow Speed
Exceptional Quality
No Cloning
1 Languages

About Tortoise TTS

Tortoise TTS is an autoregressive text-to-speech model that prioritizes audio quality above all else. Using a combination of autoregressive transformers and diffusion models, Tortoise generates extremely natural speech that captures subtle nuances of human voice. While slower than other models, Tortoise produces the most natural-sounding TTS output available.

Key Features

Ultra-High Quality

The most natural-sounding TTS output available.

Character Voices

Choose from ready-made Tortoise voices in the voice library.

Natural Prosody

Captures subtle speech patterns and micro-expressions.

Speed-Tuned Rendering

Rendered with a speed-oriented setting so clips finish in reasonable time.

Emotional Depth

Generates speech with genuine emotional resonance.

Open Source

Apache 2.0 licensed with commercial use rights.

Use Cases

Premium Audiobooks Film Production Documentary Narration Professional Voiceovers Archival Projects High-End Content

Tortoise TTS Voices

View All 18
Tortoise Angie
EN
Tortoise Deniro
EN
Tortoise Freeman
EN
Tortoise Geralt
EN
Tortoise Halle
EN
Tortoise Jlaw
EN
Tortoise Lj
EN
Tortoise Mol
EN
Tortoise Myself
EN
Tortoise Pat
EN
Tortoise Pat2
EN
Tortoise Snakes
EN

How to Use Tortoise TTS

  1. 1

    Sign up free

    Create a free TextToSpeechAI account to get starter credits. Tortoise is an Ultra-tier engine (50 credits per 1000 characters), so the free credits are perfect for a first short test.

  2. 2

    Choose a Tortoise voice

    Select one of the built-in Tortoise voices from the voice browser.

  3. 3

    Enter your text

    Type or paste the text you want narrated. Because Tortoise is slow, start with a short passage to confirm the voice and tone before sending a full audiobook chapter or long script.

  4. 4

    Generate

    Click generate and be patient. Tortoise can take from 30 seconds to several minutes per clip.

  5. 5

    Download or use the API

    When generation finishes, download your audio as MP3, WAV, or OGG, or fetch it from your history. To automate Tortoise jobs, call the TextToSpeechAI API and allow longer timeouts, since Tortoise renders slowly.

Tortoise TTS API

Generate speech programmatically using the TextToSpeechAI REST API.

curl -X POST "https://api.texttospeechai.com/v1/generate/" \
  -H "Authorization: Bearer YOUR_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "Tortoise takes its time, but the results are worth waiting for.",
    "voice": "tortoise-angie"
  }'

Frequently Asked Questions

Tortoise TTS is an autoregressive text-to-speech model created by James Betker that prioritizes audio quality above all else. It combines transformer-based language modeling with diffusion decoding to generate speech with unmatched naturalness, emotional depth, and human-like prosody. It is widely regarded as one of the most realistic open-source TTS engines available.

Yes. Tortoise TTS is open-source under the permissive Apache 2.0 license, which allows commercial use, modification, and redistribution. On TextToSpeechAI, Tortoise sits in the Ultra tier at 50 credits per 1000 characters because of its heavy compute requirements and exceptional output quality.

Tortoise is slow by design: it generates several candidate clips autoregressively and then refines the best one with a diffusion model and a CLVP re-ranking step. This quality-first pipeline means a single clip can take from 30 seconds to several minutes depending on the text length and quality preset. The tradeoff is that Tortoise produces some of the most natural speech of any TTS engine.

Not on TextToSpeechAI today. The open-source model has presets that trade speed for quality; we render with a speed-oriented setting so a clip finishes in reasonable time.

Not on TextToSpeechAI. Tortoise voices here are ready-made voices from the library. For voice cloning, use the Clone Voice tool, which runs Chatterbox.

Tortoise was trained primarily on English speech datasets, so English is where its quality is strongest. For other languages, use Piper or Bark voices, or a cloned voice.

Tortoise produces exceptional, often indistinguishable-from-human audio. It captures breathing, hesitation, intonation, and genuine emotional resonance that lighter models miss. This is why it remains a favorite for premium audiobooks, film narration, and high-end voiceover work where realism is paramount.

Tortoise typically requires 12-24GB of VRAM depending on settings and batch size, so high-end GPUs like the RTX 3090, 4090, or A100 are recommended for local use. CPU inference is technically possible but extremely slow. On TextToSpeechAI the model runs on our GPU infrastructure, so you do not need any hardware of your own.

Tortoise natively renders high-quality 24kHz WAV audio. Through TextToSpeechAI you can request MP3, WAV, or OGG, and we transcode with quality-preserving encoding so you keep the model's fine detail in whatever format your project needs.

Tortoise is in the Ultra pricing tier at 50 credits per 1000 characters, reflecting the GPU time its quality-first pipeline consumes. New accounts get free starter credits, so you can test Tortoise before committing. The Ultra tier also covers StyleTTS2.

Both are Ultra-tier engines, but they trade differently. Tortoise TTS reaches the absolute peak of naturalness and emotional depth but is by far the slowest engine. StyleTTS2 delivers near-Tortoise quality with much faster generation, making it the better choice when you need many clips or quicker turnaround. Pick Tortoise when quality is non-negotiable and time is not a constraint.

Yes. Sign up on TextToSpeechAI to receive free starter credits, then select a Tortoise voice to generate a clip without installing anything. Because Tortoise is slow, start with a short sentence before running longer jobs.

Technical Specs

  • Generation Speed Very Slow
  • Output Quality Exceptional
  • Voice Cloning Not Supported
  • Languages 1
  • GPU VRAM 12-24GB
  • Credits/1000 chars 50

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