# OpenUtau: the open source UTAU successor for singing synthesis

> OpenUtau is a free, MIT-licensed singing synthesis editor built for the UTAU community, with phonemizers for several languages, UTAU voicebank compatibility and ENUNU AI singer support. It ships as alpha builds for Windows, macOS and Linux, and it is not a digital audio workstation.

**openutau/OpenUtau** — Open singing synthesis platform / Open source UTAU successor

- Repository: https://github.com/openutau/OpenUtau
- Website: http://www.openutau.com
- Stars: 4,345 · Forks: 557
- Language: C#
- License: MIT
- Published: 2026-09-23 · Updated: 2026-09-23 · Language: en
- Canonical page: https://hysenlabs.com/projects/openutau-openutau

## What OpenUtau replaces, and for whom

OpenUtau is an editor for singing synthesis. You draw notes in a piano roll, attach lyrics and phonemes, and a resampler turns that into audio. The project describes itself as "a free, open-source editor made for the UTAU community" and as an "Open source UTAU successor", so the intended user is someone who already works with UTAU voicebanks or wants to.

The problem it addresses is friction. UTAU users historically dealt with flags instead of curves, locale switching to read Japanese file paths, and slow previews. OpenUtau replaces flags with expressions, adds phonemizers for VCV, CVVC, Arpasing and other schemes across English, Japanese, Chinese, Korean and Russian, and pre-renders vocals before playback so editing does not stall. It also runs on Windows (32/64 bit), macOS and Linux.

Two boundaries matter from the start. The README says OpenUtau can do "very minimal mixing" and will not replace a digital audio workstation, and that it does not aim for Vocaloid compatibility except for some limited features. If your workflow depends on either, this is the wrong tool.

## How rendering works: resamplers, phonemizers and pre-rendering

The architecture separates three concerns. The editor stores notes, lyrics and expressions. A phonemizer converts written lyrics into a phonetic sequence for a given language and scheme, and the repository notes that phonemizers for VCV, CVVC, Arpasing and more are included. A resampler then synthesizes audio from the phonemes and the voicebank samples.

The repository keeps built-in code in OpenUtau.Plugin.Builtin, and the README states the built-in WORLDLINE-R resampler supports curve tuning similar to many vocal synth editors. The resampling engine interface is described as versatile and compatible with most UTAU resamplers, which is how existing UTAU tooling stays usable. Pre-rendering runs synthesis ahead of playback, so tuning changes do not force a full wait on every edit.

The trade-off is visible in the file layout: cpp/ and runtimes/ sit at the top level, so the project carries native components alongside the C# application. Compatibility with third-party resamplers is a strength for UTAU users and a support burden for everyone else, since a misconfigured resampler path fails at render time rather than at install time.

## Installing OpenUtau and rendering a first phrase

The README points to prebuilt archives rather than a package manager. The download links are named OpenUtau-win-x64.zip and OpenUtau-linux-x64.zip, both attached to the latest release. The README does not document a macOS download link, a Homebrew formula, a winget package or a Flatpak, so on macOS you should check the releases page and the wiki rather than assume an installer exists.

On Windows, unzip the archive and run the executable inside it. There is no documented installer step in the README.

```bash
# Windows: unpack the release archive and run the app
# OpenUtau-win-x64.zip -> OpenUtau.exe
```

On Linux, the same pattern applies to the linux-x64 archive.

```bash
unzip OpenUtau-linux-x64.zip
cd OpenUtau-linux-x64
./OpenUtau
```

Before the first real session, the README "strongly recommended" reading the Getting-Started, Resamplers, Phonemizers and FAQ wiki pages. That is not boilerplate here: voicebank selection and phonemizer choice are what determine whether a render succeeds. The project also links a Chinese usage guide on opensynth.miraheze.org.

If you want to extend the editor rather than use it, the repository documents two APIs, an Editing Macros API under OpenUtau.Core/Editing/README.md and a Phonemizers API under OpenUtau.Core/Api/README.md. The README describes the plugin system as easy to use but gives no sample plugin in the top-level listing.

## Where OpenUtau falls short

The README is explicit that OpenUtau is not a DAW. Minimal mixing is available, but you will export stems and finish elsewhere. It also states the project does not aim to replicate UTAU features exactly, calling the compatibility "selective" and saying OpenUtau "aims to solve problems with fewer steps". A UTAU project that depends on a specific flag behaviour or an obscure plugin may not translate cleanly, and the README offers no compatibility matrix.

Release numbering is a second signal. The current builds are labelled alpha, with 0.1.570.6-alpha published on 2026-09-20 and 0.1.570.5-alpha the day before. Alpha software with frequent releases means you should expect regressions between builds and keep a known-good archive. The README does not document a rollback procedure or a stable channel.

Finally, the project is Windows- and Linux-first in its own documentation. The README lists macOS as a supported platform but provides no macOS download link, and the wiki is the only place that may explain the gap. If macOS is your only machine, verify that a current build exists before planning around OpenUtau.

## OpenUtau compared with UTAU itself

The honest alternative is UTAU, the software OpenUtau is built to succeed. The difference in approach is not feature count but design intent. UTAU tuning uses flags, and the README notes that OpenUtau replaces flags with expressions, where the built-in WORLDLINE-R resampler supports curve tuning. UTAU is also tied to the system locale for file encoding, while OpenUtau states that unlike UTAU there is no need to change your system locale.

Compatibility runs one way. OpenUtau reads UTAU voicebanks and works with most UTAU resamplers, so the sample library you already own is not wasted. What does not carry over is exact behavioural parity, which the README concedes by describing compatibility as selective. A user with a heavily tuned legacy project may find UTAU reproduces it more faithfully; a user starting fresh gets phonemizers, expression curves and pre-rendering that UTAU does not provide in the same form. ENUNU AI singers are supported through a dedicated wiki page, which is another capability with no direct UTAU equivalent.

## Licence, maintenance and the cost of upgrading

OpenUtau is MIT licensed, with LICENSE.txt at the repository root. That is permissive: you can use, modify and redistribute the code, including in closed products, provided the licence notice is preserved. It says nothing about the voicebanks you load. Voicebank licences are separate agreements, and the README does not address them, so do not read the MIT licence as covering the samples you render with.

The repository is not archived, and the last push was on 2026-09-20, the same day as the 0.1.570.6-alpha release. Development is current, but it is alpha development. Three releases landed within a week, which tells you the pace and also the churn.

Upgrade cost is therefore mostly verification. Because the project ships alpha builds and the README does not describe a rollback path, keep the archive of the version you validated. Plugin authors should track the Editing Macros API and Phonemizers API documents in the repository, since those are the interfaces a release can change under you. For everyone else, the practical cost is re-checking that your resampler and voicebank still render after an update.

## Building from source and contributing

The top-level listing shows OpenUtau.sln, a Visual Studio solution, with OpenUtau.Core as the core library, OpenUtau as the application project, OpenUtau.Plugin.Builtin for bundled plugins and OpenUtau.Test for tests. The primary language is C#. The README does not document build prerequisites, SDK versions or platform-specific build steps, so a source build means reading the solution and the GitHub Actions workflow referenced by the build badge.

There is a Windows installer script, OpenUtau.nsi, and an appcast.py at the root, which suggests update metadata is generated from the repository. The README does not explain either file.

Contribution paths are documented at a high level: report issues or suggest features on Discord or GitHub, add translations through the Crowdin project, and send fixes as pull requests. The development roadmap lives on a Trello board. If you plan to write a phonemizer or an editing macro, the two API READMEs under OpenUtau.Core are the starting point, and they are the only developer documentation the repository points to.

## Conclusion

OpenUtau suits UTAU users who want a modern editor with phonemizers, expression curves and pre-rendering, and anyone on macOS or Linux who previously had to change system locale to run UTAU. Skip it if you need a full DAW, exact UTAU behaviour or Vocaloid compatibility; the README states it does not aim for those. Before committing, check the wiki pages for resamplers and phonemizers, and try one voicebank end to end, because resampler and phonemizer setup is where most first attempts stall.

## FAQ

### Are UTAU and OpenUtau the same?

No. OpenUtau is a separate editor described as an open source UTAU successor, with selective backward compatibility. It reads UTAU voicebanks and works with most UTAU resamplers, but the README states it is not designed to replicate UTAU features exactly.

### Is OpenUtau free?

Yes. The repository is licensed under MIT and the README describes OpenUtau as free and open source. That licence covers the software, not the voicebanks you load into it.

### What is OpenUtau?

It is an open source singing synthesis editor made for the UTAU community, written in C# and running on Windows, macOS and Linux. It provides a MIDI editor, phonemizers for several languages, expression-based tuning and pre-rendering.

### How do I install OpenUtau?

Download the release archive from the project's releases page, either OpenUtau-win-x64.zip or OpenUtau-linux-x64.zip, unpack it and run the executable. The README does not document a macOS download link or a package manager install.

### Does OpenUtau work on macOS?

The README lists macOS among the supported platforms, alongside Windows 32/64 bit and Linux. However, the download badges in the README only cover windows-x64 and linux-x64, so check the releases page for a current macOS build.

## Sources

- [License: MIT](https://github.com/openutau/OpenUtau/blob/master/LICENSE)
- [openutau/OpenUtau on GitHub](https://github.com/openutau/OpenUtau)
- [Project website](http://www.openutau.com)
- [README](https://github.com/openutau/OpenUtau/blob/master/README.md)
- [Releases](https://github.com/openutau/OpenUtau/releases)

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Hysen Labs editorial analysis, written from the project's own repository and release notes. Cite the canonical page: https://hysenlabs.com/projects/openutau-openutau