[Free/Paid] Summary of Speech Synthesis Engines from Various Companies. Introducing which software uses which engine.

Currently, many text-to-speech software applications have been released.

However, when listening to the audio from text-to-speech software, you might sometimes feel, "Wait, isn't this voice tone the same as other software?"

In fact, text-to-speech software requires a base speech synthesis engine.

Therefore, even if the software names are different, if the speech synthesis engine is the same, the voice tone will be the same.

In this article, we will introduce speech synthesis engines that can be used for free and those that can be used for a fee.

We will also include information that might make you think, "Oh, that software was using this synthesis engine!"

Please take a look!

Speech synthesis engines that can be used for free

Free text-to-speech software mainly uses the following speech synthesis libraries and engines:

• AquesTalk
• Open JTalk

These are the speech synthesis libraries and engines being used.

AquesTalk

Developed by AQUEST Co., Ltd., AquesTalk is known for "Yukkuri Voice" and "Bouyomi Voice."

All software capable of reading in the voice tone commonly referred to as "Yukkuri" utilizes "AquesTalk."

Representative examples include Bouyomi-chan and SofTalk.

Because synthetic voices can be easily created from text, it is used in various situations from personal use to commercial products.
In addition to being used as the base for SofTalk and Bouyomi-chan, it is also used for sampling in the default voice of UTAU. Furthermore, it is used for guidance voices in home appliances such as telephones.

AquesTalk was first released on May 25, 2006. The development period was reportedly just under two years. (AquesTalk Release exit)
The sound source is not created by recording but by manually manipulating parameters; it is a pure synthetic voice with no "person inside."

In January 2010, the successor version, AquesTalk2 exit, was announced.
It supports a wide range of platforms including Windows, Mac OS X, WinCE, iPhone, Android, and other smartphones. Recently, an independent microchip (hardware) called AquesTalk pico has also appeared.

Source: Nico Nico Pedia

Because API usage licenses and development libraries are provided, it can be used for various purposes if you have programming skills.

For details, please check the company's website.

AquestTalk

Yukkuri Voice is also explained in this article.

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Open JTalk

Open JTalk is a Japanese text-to-speech system developed at the Tokuda-Lee Lab of the Nagoya Institute of Technology.

It is open-source, distributed under the Modified BSD License.

"Open JTalk" is used in Texter. If you hear it once, you might feel like you've "heard it before."

Open JTalk

Speech synthesis engines that can be used for a fee

Famous paid speech synthesis engines include:

• IBM: Watson Text to Speech
• Google: Text to Speech
• Amazon: Polly
• Microsoft: SAPI5

There are many attractive plans, such as being free for up to tens of thousands of characters.

Demos for the paid speech synthesis engines mentioned above are provided on their websites, allowing you to play and listen to the voices.

Speech synthesis engines have a high difficulty level

In this article, we introduced speech synthesis engines.

By using a speech synthesis engine, you can create your own text-to-speech software or finish it as text-to-speech software customized to your liking.

However, when you actually try to use them, since they are provided as APIs, the setup is difficult if you cannot program.

API stands for "Application Programming Interface" and refers to "sharable programs specialized for a single function" or "a mechanism for sharing software functions." If frequently used functions are prepared as APIs, there is no need to write a program from scratch. You can utilize APIs as needed to proceed with development efficiently.

In the case of a Web API, the program is published on the web and utilized by calling it from outside. Web APIs are published in various fields, and many Web APIs can be used for free.

For example, if you can obtain the latest information from another company's site via an API, you can add new functions to your own website or app to improve the service. In recent years, the level required for smartphone apps has increased, so using Web APIs in app development has become common.

Source: internet academy

Companies that provide paid versions of text-to-speech software either develop their own proprietary speech synthesis engines or use the paid speech synthesis engines introduced here.

"Wait, why not just make a speech synthesis engine from scratch?"

You might think so, but this is not an easy task.

It would be a task requiring a difficult process with many researchers, developers, and funding.

At the very least, it is difficult for an individual and is not realistic unless it is on the scale of a company or a research institution.

Therefore, if you find using APIs difficult, using paid text-to-speech software is more intuitive and easier to handle.

Many types of text-to-speech software have been released, ranging from free to paid versions.

I am sure you will find your favorite software.

They are summarized in detail in this article, so please check it out!

【2025 Latest】10 Recommended Text-to-Speech Software! Introducing Free Software Available for Commercial Use | Text-to-speech software Ondoku

A comparison of recommended text-to-speech software! Carefully introducing tools from browser-based ones that require no installation to high-performance desktop types, including free tools available for commercial use.

I hope this article is helpful to you.

We look forward to seeing you again.

■ AI voice synthesis software "Ondoku"

"Ondoku" is an online text-to-speech tool that can be used with no initial costs.

• Supports approximately 50 languages, including Japanese, English, Chinese, Korean, Spanish, French, and German
• Available from both PC and smartphone
• Suitable for business, education, entertainment, etc.
• No installation required, can be used immediately from your browser
• Supports reading from images

To use it, simply enter text or upload a file on the site. A natural-sounding audio file will be generated within seconds. You can use voice synthesis up to 5,000 characters for free, so please give it a try.

Text-to-speech software "Ondoku" can read out 5000 characters every month with AI voice for free. You can easily download MP3s and commercial use is also possible. If you sign up for free, you can convert up to 5,000 characters per month for free from text to speech. Try Ondoku now.

HP: ondoku3.com
Email: ondoku3.com@gmail.com