Realistic Text-to-Speech Voice Synthesis: Comparing Tortoise and Bark

Text-to-speech (TTS) technology has seen rapid advances thanks to recent improvements in deep learning and generative modeling. Two models leading the pack are and . Both leverage cutting-edge techniques like transformers and diffusion models to synthesize amazingly natural-sounding speech from text. Bark Tortoise TTS For engineers and founders building speech-enabled products, choosing the right TTS model is now a complex endeavor, given the capabilities of these new systems. While Bark and Tortoise have similar end goals, their underlying approaches differ significantly. This article will dive deep into how Bark and Tortoise work under the hood, their respective strengths and weaknesses, and when each one is the superior choice. Whether you're developing a voice assistant, synthesizing audiobook narration, or exploring new generative frontiers in audio, understanding these models is key to success. By the end, you'll clearly understand which model aligns best with your needs and constraints when bringing next-gen TTS into your products. You'll also learn about some other text-to-audio models you can check out. Let's get started! Use cases and capabilities Let's take a high-level look at what each model can do before we get into a more detailed comparison. All about Bark Bark is a text-to-audio generative model created by Suno AI. It utilizes a transformer architecture to generate high-quality, realistic audio from text prompts. Some key capabilities of Bark: It can synthesize natural, human-like speech in multiple languages. This makes it suitable for voice assistant applications, audiobook narration, and more. Beyond just speech, Bark can also generate music, sound effects, and other audio. This flexibility enables creative use cases like producing customized audio for videos, games, or interactive apps. The model supports generating laughs, sighs, and other non-verbal sounds to make speech more natural and human-sounding. Check out an example . I find these really compelling, and these imperfections make the speech sound much more real. here (scroll down to "pizza.webm") Bark allows control over tone, pitch, speaker identity, and other attributes through text prompts. This level of control is useful for developing distinct voice personas. It requires no additional data annotation beyond text transcripts. The model learns directly from text-audio pairs. In summary, Bark is a powerful generative model capable of synthesizing high-quality speech and diverse audio entirely from text. Its flexibility enables a range of potential applications from voice assistants to audio production tools. Note: you can use Bark to produce non-speech sounds like sound effects. This is similar to . another model called AudioLDM, which we have a guide for here Bark's inputs and outputs Here's a breakdown of the inputs and outputs for the Bark , using data from the . model implemented by Suno on Replicate.com API spec page Inputs: (string): The input prompt that provides the initial context for the generation. The default value is "Hello, my name is Suno. And, uh — and I like pizza. [laughs] But I also have other interests, such as playing tic tac toe." prompt (string): A choice for audio cloning history. This allows you to choose from a list of predefined speaker IDs in various languages (e.g., en_speaker_0, es_speaker_1, fr_speaker_2, etc.). This history helps the model understand the voice style to generate audio in. history_prompt (file): If provided, this .npz file overrides the previous setting. You can provide your own history choice for audio cloning. custom_history_prompt history_prompt (number): Generation temperature for the text generation process. A higher value (e.g., 1.0) makes the output more diverse, while a lower value (e.g., 0.0) makes it more conservative. The default value is 0.7. text_temp (number): Generation temperature for the waveform generation process. Similar to , this parameter affects the diversity of audio generation. The default value is 0.7. waveform_temp text_temp (boolean): If set to , the model returns the full generation as a .npz file, which can be used as a history prompt for future generations. output_full true Outputs: The model's output structure is described by the following JSON schema: { "type": "string", "title": "Output", "format": "uri" } Some additional details you may find helpful: (string): A URI that points to the generated audio file. This is the primary output of the model, containing the audio representation of the generated text prompt. audio_out (string): A URI that points to the .npz file representing the prompt used for generating the audio. This can be useful for keeping track of the input context that led to the audio generation. prompt_npz In summary, the Bark model takes input prompts, history choices, and generation temperature settings to produce audio output. The output includes a link to the generated audio file and a link to the .npz file representing the prompt. All about Tortoise TTS Tortoise TTS is a text-to-speech model optimized for exceptionally realistic and natural-sounding voice synthesis. It was created by James Betker. Key capabilities of Tortoise TTS: It excels at cloning voices using just short audio samples of a target speaker. This makes it easy to produce text in many distinct voices. The quality of the synthesized voices is extremely high, nearly indistinguishable from human speakers. This makes Tortoise great for use cases like audiobook narration. Tortoise supports fine-grained control of speech characteristics like tone, emotion, pacing, etc, through priming text. This flexibility helps bring voices to life. The model efficiently leverages smaller datasets by training an autoencoder for voice compression. Less data is needed relative to other TTS models. Tortoise focuses specifically on speech synthesis. While it lacks flexibility for music or sound effects, it provides unparalleled realism for voice. In summary, Tortoise TTS is an exceptionally high-fidelity text-to-speech model optimized for cloning voices and narrating long-form speech content like books or articles. The quality and control it provides over voice synthesis makes Tortoise suitable for a range of applications from virtual assistants to audiobook creation. You can even use Tortoise to create voice clones of celebrities like Barack Obama, Donald Trump, Walter White, Tony Stark, and more! Tortoise TTS's inputs and outputs Here's an overview of the inputs and outputs for the Tortoise model, again looking at the , this time by creator . implementation on Replicate afiaka87 Inputs: (string): The text input that you want the model to generate speech for. The default value is "The expressiveness of autoregressive transformers is literally nuts! I absolutely adore them." I am not sure why that's the default... but it is! text (string): Selects the primary voice to use for speech generation. You can choose from a list of predefined voices (e.g., angie, deniro, halle, etc.) or use special values like , , or . The default value is , which selects a random voice. voice_a random custom_voice disabled random (file): If provided, this file should contain an mp3 audio of a speaker that you want to use as a custom voice. The audio should be at least 15 seconds long and only contain one speaker. This parameter overrides the setting. custom_voice voice_a and (strings, optional): These parameters allow you to create a new voice by averaging the latents of the selected voices. You can choose from predefined voices or use to disable voice mixing. These parameters are optional. voice_b voice_c disabled (string): Specifies a voice preset to use for generation. The preset determines the quality and speed of the generated speech. Allowed values are , , , and . The default value is . preset ultra_fast fast standard high_quality fast (integer): A random seed that can be used to reproduce results. The default value is 0. seed (number): Determines how much the CVVP (Concatenative Voice Variational Posterior) model should influence the output. Increasing this value can reduce the likelihood of multiple speakers in the generated speech. The default value is 0 (disabled). cvvp_amount Output: The model's output structure is described by the following JSON schema: { "type": "string", "title": "Output", "format": "uri" } The output is a URI (Uniform Resource Identifier) that points to the generated speech audio file. This audio file represents the synthesized speech based on the provided input text and voice settings. In summary, the Tortoise TTS model takes input text, voice selections, preset options, and other parameters to generate speech. The output is a URI pointing to the audio file containing the generated speech. Comparing Bark and Tortoise TTS Now that we've seen what kind of inputs and outputs the models work with let's take a comparative look across a number of different dimensions: Architecture Speech generation ability Language Accents Output quality By the end of the article, you'll understand when to use Bark and when to use Tortoise. We'll also look at some other models you may want to check out, so you can find the proper fit for your use case. Model Architecture The architecture used by a TTS model impacts what it can generate and how well it performs. Understanding these technical differences helps interpret the strengths and limitations of building products with them. The key differences between Bark and Tortoise: that can generate diverse sounds like music. But it requires huge amounts of varied training data. Bark uses a flexible transformer architecture . But this specialization makes it harder to expand to other sounds. Tortoise uses custom components focused specifically on reproducing human voices realistically Looking closer, Bark employs a architecture similar to GPT-3, as described in the . It embeds text into abstract tokens without phonemes. A second transformer converts these into audio codec tokens to synthesize the waveform. Transformers leverage self-attention to model relationships in data, enabling generative capabilities. This provides flexibility in sounds like music but needs lots of data for high fidelity. transformer README Tortoise uses a -style encoder-decoder for text and an for audio compression. It then decodes compressed audio using a , as described in the . Tacotron autoencoder diffusion model paper This specialized configuration targets voice realism. The autoencoder clones voices efficiently. The diffusion model gives Tortoise exceptional quality. The tradeoff is less flexibility than Bark. These architectural differences have implications for product possibilities. Bark offers flexibility for apps with diverse audio needs. Tortoise prioritizes voice quality for use cases like audiobooks. Understanding these strengths and weaknesses helps you pick the right model for your needs. Voice Customization The ability to customize and control the synthesized voice is important for some applications. You'll need to decide how important it is for yours because Bark and Tortoise take different approaches to enabling voice control. but no straightforward way for end users to clone new voices. As described in the documentation, Bark supports 100+ speaker presets across languages. These allow controlling attributes like tone, pitch, and emotion. However, adding new custom voices requires advanced technical skills. Bark has a limited set of built-in voice presets In contrast, using just short audio samples. Its autoencoder compression enables efficient capturing of speaker characteristics. As explained in the , users can clone voices by providing a few audio clips of a target speaker. Tortoise excels at cloning voices source code repo for Suno's implementation For simple voice assistant applications with a limited set of voices, Bark's presets may suffice. But for product ideas requiring extensive voice cloning of arbitrary speakers, Tortoise is likely the better choice despite additional complexity. Supported Languages and Accents Bark and Tortoise take different approaches to supporting multiple languages and accents, with implications for product localization and access. Bark supports many languages relatively well out of the box, as listed in the documentation: - English (en) - German (de) - Spanish (es) - French (fr) - Hindi (hi) - Italian (it) - Japanese (ja) - Korean (ko) - Polish (pl) - Portuguese (pt) - Russian (ru) - Turkish (tr) - Chinese, simplified (zh) Bark handles code-switching and accents smoothly, automatically detecting the language from the text prompt. In contrast, Tortoise was trained mostly on English data. As explained in the paper, it lacks diversity in supported languages and accents. Non-English speech would require collecting additional training data and retraining the models. This gives Bark an advantage for products aimed at global markets or supporting multilingual users. Bark's built-in multilingual support reduces the effort required for localization. Tortoise would involve more work to expand beyond English. For products highly optimized for a single language, like English audiobooks, Tortoise provides superior quality. But Bark is generally a better choice if easily supporting many languages and accents is critical. Output Quality While both models produce excellent results, Tortoise TTS edges out Bark in default audio quality right out of the box. However, Bark can match Tortoise given sufficient tuning and prompt engineering. As noted in the documentation, Bark's audio quality is very good, but some creative prompting is needed to achieve the best results. Guiding the model with brackets, capitalization, speaker tags, and other markup can improve fidelity. You may also need to post-process some audio if super-high-quality sound is important to your use case. In contrast, Tortoise offers exceptional audio quality without any prompt tuning needed. Synthesized voices are extremely close to human speech. The samples sound virtually indistinguishable from real people, with only a few artifacts. This difference highlights Tortoise's focus specifically on optimizing voice reproduction. The diffusion model and conditioning workflow deliver consistently amazing results unmatched by other TTS systems. However, Bark's flexibility as a general audio model means it can likely match Tortoise's quality given enough experimentation with prompts. This prompt tuning requires more effort and skill. I haven't spent enough time with it to pull this off, but you may be able to. In summary, Tortoise exceeds Bark in default out-of-the-box output quality. But Bark can achieve equivalent quality with sufficient prompting expertise at the cost of additional effort. Building Startups with Bark and Tortoise Both Bark and Tortoise enable the creation of a wide range of speech-focused products. What kind of products could you build with these tools? Here are some example startup ideas that play to the strengths of each model: Bark Voice assistant service supporting multiple languages - Bark's built-in multilingual capabilities make it easy to build assistants for global markets. Interactive audio games - Bark's flexibility allows for generating sound effects, background music, and dialogue on the fly. Foreign language learning apps - Combine Bark's speech synthesis with language education tools. Tortoise Hyper-realistic voice cloning service - Clone customer voices or famous voices using Tortoise's exceptional quality. Synthetic voice actors - Use Tortoise to easily craft distinct voices for animation/video content. Automated audiobook creation - Produce audiobooks from ebooks leveraging Tortoise's strengths in long-form narration. Personalized guided meditations - Generate customized meditation audio in your own voice with Tortoise. Both Custom text-to-speech APIs - Offer TTS as a service focused on quality and voice control. Text-to-podcast service - Automatically convert blog posts into podcast episodes with Bark's audio generation skills. Text-based adventure games - Immerse players with reactive voice narration and effects. Accessibility tools - Enable those with disabilities to convert text to realistic speech. The quality and voice control of Bark and Tortoise opens up many new product possibilities spanning entertainment, education, accessibility, and productivity. What are you going to build with these tools? Comparing Bark and Tortoise to Alternative TTS Models While this article has focused on Bark and Tortoise TTS, there are a few other leading text-to-speech models worth considering: is a latent diffusion model created by Haoheliu focused on generating high-quality audio from text transcripts. It produces very realistic voices and speech like Bark and Tortoise. However, it lacks the flexibility of Bark for non-speech audio and the exceptional voice cloning capabilities of Tortoise. AudioLDM is a speech recognition model originally created by OpenAI and now maintained by Anthropic. It specializes in transcribing audio-to-text rather than text-to-audio generation. This makes it complementary to the other models. Whisper by Jagilley is an audio-to-audio voice conversion model. It can alter and convert voices while retaining the same speech patterns and style. This can be used along with TTS models like Tortoise that support voice cloning. Free VC While Bark and Tortoise are good choices, these alternative models can provide complementary capabilities like speech-to-text, easier voice cloning, and voice style transfer to consider when building voice-enabled products. They might be a better fit for your product, depending on its needs. Note: If you're shopping around for the right model, you can also and get a recommended set of models based on their similarity to your exact use case. describe your project here Here is a comparison of the text-to-speech models Bark, Tortoise TTS, AudioLDM, Whisper, and Free VC across different use cases and product applicability: For voice assistant applications, is likely the best option, given its built-in multilingual capabilities and flexibility in generating sound effects and music in addition to speech. and also work well for voice assistants focused just on speech realism. Bark Tortoise TTS AudioLDM For audiobooks and long-form speech synthesis, is likely the best choice, given its exceptional voice cloning capabilities and natural prosody. and can also work well but may require more tuning. Tortoise TTS Bark AudioLDM For transcribing speech to text, is purpose-built for this use case and would be the recommended model. Whisper For voice cloning and conversion, specializes in this capability, making it the best fit. Tortoise TTS also enables voice cloning via samples. Free VC The table below summarizes the various use cases I discussed above. Model Best Use Cases Key Strengths Bark Voice assistants, audio generation Flexibility, multilingual Tortoise TTS Audiobooks, voice cloning Natural prosody, voice cloning AudioLDM Voice assistants High-quality speech Whisper Transcription Accuracy, flexibility Free VC Voice conversion Retains speech style Each model has strengths making them best suited for certain use cases and products, though there is also overlap in capabilities across models. Experiment to find the right one! Conclusion Text-to-speech technology has advanced rapidly, providing startups with many options for building voice-enabled products. While Bark and Tortoise are good choices, alternatives like AudioLDM, Whisper, and Free VC provide complementary capabilities to consider. The key is picking the right model for your specific use case and constraints. For multi-language voice assistants, Bark is likely the top contender. Tortoise excels at hyper-realistic audiobook narration and voice cloning. And there are other applications for which either model could be used. I hope this guide provides a solid foundation for choosing the right text-to-speech model for your next product. Let me know if you have any other questions! I'm always happy to help interpret the landscape of generative AI models to build amazing new applications. Thanks for reading. Resources and Further Reading You may find these links helpful as you learn more about the world of generative text-to-speech models. - Details on model architecture, examples, installation, and usage Bark GitHub repo - Source code, documentation, and usage guide Tortoise GitHub repo - Technical details on model architecture and training Tortoise TTS paper - Info, pricing, and hosted API access Bark model on Replicate - Info, pricing, and hosted API access Tortoise model on Replicate - What makes this model special? What can you build with it? An in-depth guide to creating sound and speech from text or audio files using AudioLDM text-to-audio. A builder's guide to synthesizing sound effects, music, and dialog with AudioLDM - Tips for generating longer audio Notebook on long-form Bark generation - High-level capabilities and use cases AIModels overview of Bark - High-level capabilities and use cases AIModels overview of Tortoise TTS - Browse other related models. Supply your use case and get a list of candidate models to try out. TTS models on AIModels Also published . here