UTAlet is a browser-based voice synthesis tool using UTAU voicebanks.
It is designed to work with both CV (Consonant-Vowel) and VCV (Vowel-Consonant-Vowel) voicebanks.

Only voice sources with permission from the voice rights holder may be used.

Core synthesis software

• Official UTAU (飴屋／菖蒲)
• OpenUtau (stakira)

Related projects

• Voicebank configuration tool: Laberu
• Voicebank packaging tool: Gakuya

Page links

• Open Video Editor

Third-party tools

• Recording tool: RecStar (sdercolin)
• Project file converter: UtaFormatix (sdercolin)

2026/06/27
When oto.ini has empty parameters, they are now read as 0.

2026/06/14
[Add] Expanded background features in the Video Editor.
[Add] Added lyric display support in the note info panel of the Video Editor.
[Fix] Added controllable piano-roll FPS in the Video Editor, and set the default to a speed that keeps lyrics readable.

2026/06/06
[Add] Added the dedicated Video Editor page.
[Add] Added more background pattern variations in the Video Editor.
[Add] Added control over title/credit display timing in the Video Editor.
[Add] Expanded piano-roll related features in the Video Editor.
[Fix] Adjusted the Video Editor layout.

2026/05/27
[Fix] Fixed an issue where notes with $Direct=true were not played back correctly.

2026/05/17
[Fix] Fixed an issue where the piano roll could not be rendered correctly when the effective note length became negative due to negative overlap, etc.
[Fix] Fixed an issue in the note property dialog where pre-utterance and overlap could not be reset.
[Fix] Adjusted playback/download behavior when non-contiguous notes are selected. When a backing track is set or when downloading, notes are always treated as a contiguous range.

2026/05/16
[Fix] Fixed an issue where vibrato was not rendered correctly in some cases on the piano roll.
[Fix] Reviewed the default value of "Apply light vibrato to all notes" in "Automatic Preprocessing".

2026/05/06
[Add] Added audio waveform to the video creation feature.
[Add] Added a lyrics card loading feature to the video creation feature.
[Add] Added the ability to zoom in/out the piano roll display scale in the video creation feature.
[Fix] Fixed an issue where the note font size in the preview screen of the video creation feature was incorrect.
[Fix] Adjusted the layout.

2026/05/05
[Add] Added piano roll to the video creation feature.
[Fix] Fixed an issue where the preview scale in the video creation feature could differ from the actual exported video.
[Fix] Fixed an issue where synthesis-wait progress was not displayed correctly when all WAV files were already cached.

2026/05/04
[Add] Made it possible to adjust each parameter of the simple mix function.
[Add] Added batch flag setting, batch voice color setting, transpose by specific pitch, and shift by specific scale degree to batch processing.
[Fix] Fixed an issue where 32-bit WAV files could not be loaded in accompaniment.

2026/05/03
[Add] Backgrounds other than solid color are now available in the video creation feature.
[Add] Added decorations applicable to title/credit text in the video creation feature.
[Add] Added lyric subtitle display based on UST data in the video generation feature.

2026/05/02
[Add] Added a simple video creation feature. Only thumbnail settings are supported, but the output can be exported in video format.

2026/05/01
[Add] Added a simple mix feature. While mixing should ideally be done in a DAW, you can now output vocals combined with a backing track. Harmonies and similar features are not supported.

2026/04/11
[Add] Added new flags
O flag: default 0, range -100 to 100, mouth opening/closing
T flag: default 0, range -100 to 100, tension
S flag: default 0, range -100 to 100, formant emphasis (clearness/sharpness)
b flag: default 0, range -100 to 100, brightness
Mo flag, same as O flag (for UST files created for moresampler)
Mt flag, same as T flag (for UST files created for moresampler)
MG flag, same as w flag (for UST files created for moresampler)
ME flag, same as S flag (for UST files created for moresampler)
[Fix] Revised the processing of the B flag.

2026/04/07
[Fix] When loading some configuration files fails, only that file is ignored and loading continues.
[Fix] Fixed an issue where, if some pitches are missing in prefix.map, pitches above the missing ones now work correctly.

2026/04/06
[Fix] Fixed an issue where empty lines in presamp.ini prevented the file from being loaded.

2026/03/27
[Fix] When icon/sample file paths in character.txt or portrait path in character.yaml are invalid, the app now skips only those invalid entries and continues loading the voicebank.

2026/03/20
[Fix] When loading a voicebank that contains an invalid character.yaml, the app now ignores character.yaml and continues loading the voicebank.

2026/03/07_2
[Fix] Fixed an issue where voicebank names written as Japanese `名前` in character.txt could not be read correctly.

2026/03/07
[Added] Added a batch process to randomize pitch
[Fix] Fixed an issue where middle-click opened the note menu on PC.

2026/03/06
[Fix] Fixed an issue where saving the project tempo as empty stored an invalid value.
[Fix] Fixed an issue where tempo info was missing when exporting a UST after setting tempo on the first note.

2026/02/16
[Added] Added event announcement to the top page

2026/01/08
[Fix] Fixed an issue where voice bank configuration files could not be loaded despite correct folder placement, depending on the zip environment

2026/01/06
[Added] Added prefix.map tab to voice bank information dialog

2026/01/05_2
[Fix] Enhanced voice bank diagnostics

2026/01/05
[Fix] Fixed an issue where oto.ini files from other folders were incorrectly loaded under certain conditions, when only oto.ini files under character.txt folder should be loaded

2026/01/04_2
[Fix] Fixed an issue where oto configuration data loaded with the previous encoding remained when changing the character encoding in the voice bank info dialog
[Fix] Fixed an issue where the diagnostics process would stop when corrupted FRQ files exist

2026/01/04
[Added] Countermeasure for app crashes when using browser's auto-translation feature
[Added] Enhanced error display content when voice bank loading fails
[Added] Added alias list tab to voice bank dialog
[Added] Added diagnostics tab to voice bank dialog

2026/01/03
[Added] Added accompaniment-only playback feature. You can play only the selected range or play from the end of notes.
[Fix] Fixed an issue where 48000Hz stereo accompaniment data could not be played
[Fix] Fixed an issue where accompaniment would not play when moving the playback position in the positive direction

2026/01/02
[Added] Added pitch snap to scale feature to batch processing
[Added] Temporarily added Japanese presamp to phonemizer (under development)
[Fix] Adjusted log granularity

2025/12/31
[Fix] Adjusted color themes. Previous color themes are retained as legacy themes.

2025/12/28
[Fix] Fixed an issue where scrolling would not be restored after pitch editing.
[Fix] Fixed an issue where loading UST files without flags could result in flags being set to 'undefined', causing them to be recognized as the 'e' flag.

2025/12/24
[Fix] Fixed a bug where an error occurred when using the phonemizer "(Japanese) Automatic VCV(with CVVC)" if the VC oto entry existed but the CV oto entry did not.

2025/12/18
[Fix] Fixed an issue where undo/redo did not work correctly when changing an alias or note length from the note long-press menu

2025/12/17
[Added] Added pitch pattern feature

2025/12/16
[Fix] Internal processing improvements.

2025/12/14
[Fix] Fixed an issue where undo history was not cleared when initializing a project.

2025/12/09
[Fix] Fixed a bug where the editor could not even be opened when there was a note with invalid parameters.

2025/12/07
[Fix] Fixed an issue where synthesis failed if the offset in Oto settings was a negative number.

2025/12/06
[Fix] Fixed an issue where modulation could not be saved.

2025/12/05
[Fix] Resolved an issue where settings items conflicted with other Kimigatame tools.

2025/12/03
[Added] Added a feature to select all notes by double-tapping an empty area when no notes are selected.

2025/12/01
[Added] Added format-specific paste feature to the note long-press menu.
[Added] Implemented Japanese automatic CVVC mode with Romaji input support.
[Fix] Fixed an issue where waveform display was incorrect when converting lyrics to CVVC.

2025/11/30
[Added] Added phrase selection button to the note long-press menu.
[Added] Added note length selection feature to the note long-press menu.
[Added] Added features to batch processing: apply Oto settings, apply Auto-Fit results, and convert lyrics to rest.
[Fix] Revised accompaniment synchronization playback method.
[Fix] Made it impossible to change accompaniment settings during playback or synthesis.
[Fix] Made accompaniment mute status easier to understand.

2025/11/28
[Added] Added cache clear button to the note long-press menu.
[Added] Added character portrait toggle button to the project menu.
[Added] Double-tapping an empty area now cancels note selection.
[Fix] Fixed a bug in batch process: Automatic Preprocessing.
[Fix] Revised accompaniment synchronization playback process.

2025/11/27_2
[Fix] Fixed a bug where ust files could not be loaded if there was even one note without pitch set.

2025/11/27
[Fix] Fixed an issue where pitch editing did not work correctly when the piano roll was vertically zoomed.
[Fix] Fixed a bug where adding pitch portamento after a rest could result in invalid values.
[Fix] Revised the display range of the piano roll.

2025/11/25
[Added] Added note length quantization feature to batch processing.

2025/11/24
[Added] Added scale specification feature in the project menu.
[Added] Piano roll colors now change according to the scale.
[Added] Added "Add characters to the end of lyrics" and "Remove characters from the beginning/end of lyrics" to batch processing
[Fix] Fixed a bug where undo/redo could not be used after changing lyrics via double-tap.
[Fix] Added missing language resources

2025/11/23_2
[Fix] Removed pinch-in and pinch-out functionality due to significant related issues

2025/11/23
[Added] Added pinch-in and pinch-out zoom functionality.
[Fix] Resolved issues related to pitch portamento.

2025/11/16
[Added] Added experimental BPM auto-detection feature.
Added automatic timing adjustment feature for accompaniment tracks.

2025/11/15_3
[Fix] Fixed an issue where swipe scrolling during pitch editing was not disabled on iOS environments.

2025/11/15_2
[Fix] Fixed a bug where abnormal values could contaminate pitch data, causing pitch lines to fail to render.

2025/11/15
[Fix] Made it possible to grab and edit portamentos in the envelope editor.
[Fix] Made it possible to grab and edit portamentos in pitch editing mode. Note that screen scrolling via swiping is now locked when a portamento is selected.
[Fix] Fixed a bug where portamentos could not be added properly when there were only 2 pitch portamentos.
[Fix] Fixed a bug where batch lyric change processing did not work properly when rests were included.
[Fix] Fixed a bug where automatic lyric conversion did not work when editing lyrics via double-tap.

2025/11/09
[Added] Added accompaniment track feature. You can load wav files for waveform display and simultaneous playback.

2025/11/08
[Fix] Fixed an issue where it was difficult to input when trying to leave some numeric input fields blank, as the minimum value would automatically be entered.
[Added] Added voice color feature (OpenUtau compatible).
You can output ust including voice color, but the official UTAU will ignore the voice color value.
[Fix] Enhanced logging

2025/11/03
[Added] Added batch lyric change feature to batch processing. Hiragana input is split by syllable, alphanumeric input is split by space.
[Added] Experimental support for Japanese automatic mode (CVVC). It will be monitored for a while, and if there are few issues, it will become a standard feature.

2025/11/02
[Added] Added sine wave sound when placing notes.
$direct=true can now be set in the note properties.

2025/10/29
[Fix] Fixed an issue where projects could not be reopened when the score data from the previous session contained rests shorter than the preutter of the following note

2025/08/20
[Fix] Improved engine and voice library loading process

2025/08/03
[Feature Added] Added flag feature.
w flag, default: 0, range: 0–100, growl strength

2025/07/26
[Feature Added] Added support for Portuguese display and character encoding.

2025/07/15
[Feature Added] Added alias selection functionality to the long-press menu for notes.
Implemented Japanese automatic VCV mode with Romaji input support.
Japanese automatic VCV mode is now a standard feature.

2025/07/13
[Feature Added] Added waveform display functionality.
Theme colors can now be changed.

2025/07/09
[Feature Added] You can now change the number of resamplers from the header.
In mobile environments, 3 is usually optimal.
For low-spec environments, try 1 or 2.
Conversely, increasing the number speeds up processing on PC environments.
[Fix] Fixed an issue where sounds containing voiced marks did not play correctly when selecting a sound source folder on macOS or iOS environments.

2025/07/07
[Feature Added] Added Japanese automatic VCV mode. It will be monitored for a while, and if there are few issues, it will become a standard feature.

2025/07/04
[Fix] Fixed an issue where certain WAV files could not be loaded.

2025/07/03
[Fix] Disabled translation functionality to prevent app crashes caused by browser auto-translation tools.

2025/06/20
[Added] Support for Chinese display and character encoding.

2025/06/10
[Fix] Added automatic restart feature when engine startup fails

2025/06/09
[Fix] Fixed an issue where files in the top-level folder could not be loaded correctly.
Flags containing '+' are now supported.

2025/06/08
[Fix] Fixed an issue where certain WAV files could not be loaded.
Fixed an issue where a '?' indicator was always shown on rests.

2025/06/07
[Feature Added] Added a '?' indicator when an alias does not exist.
Enabled lyric editing by double-tapping a note.

2025/06/05
[Fix] Fixed an issue where a long press on the editor unintentionally enabled selection.

2025/06/04
[Fix] Fixed an issue where a long press on the editor unintentionally enabled selection.

2025/05/28
[Fix] Improved compatibility with UST files containing invalid parameters

2025/05/23_2
[Feature Addition] Added functionality to automatically continue the project that was being edited previously
Added a project initialization button
Added new links

2025/05/25
[Fix] Improved compatibility with UST files containing invalid parameters

2025/05/18
[Feature Added] Flag functionality has been implemented.
g flag, default: 0, range: -100 to 100 — controls voice gender
B flag, default: 50, range: 0 to 100 — controls breathiness; setting it to 0 or 100 speeds up synthesis
t flag, default: 0, range: -100 to 100 — pitch correction in cents
P flag, default: 86, range: 0 to 100 — adjusts peak compressor intensity
G flag, no value — regenerates the frequency table at each playback
e flag, no value — switches the engine's time-stretching method to loop-based

2025/05/17
[Fix] Improved compatibility with UST files containing invalid parameters

2025/05/16
[Fixes] Fixed a bug where oto.ini files starting with Charset:UTF8 could not be loaded.
[Feature Additions] Enabled selection of .uar files when choosing ZIP files.

2025/05/06
[Feature Additions] Added functionality to load voicebanks from a folder. Please select a folder that contains a character.txt file.

2025/05/04
[Added] Added tempo and label editing features to individual notes, and enabled displaying tempo and labels.
[Fixes] Fixed an issue where long USTs might not play back correctly.

2025/05/02
[Fixes] Fixed an issue in the TSURU engine where certain sounds would incorrectly resemble death growls. Also fixed a bug in the batch auto-processing where lyrics containing `ゅ` or `ょ` were not converted correctly.

2025/04/23
[Fixes] Fixed a bug where invalid values were injected into the output UST

2025/04/13
[Fixes] Fixed the bug where voicebank names became garbled after 4/12
Fixed the bug where the note editing screen became unplayable after 4/12
Changed the default language to reference the browser settings

2025/04/12
[Feature Additions]
Added dotted quarter note and dotted eighth note to the note addition feature

[Fixes]
Fixed bug where setting consonant velocity and volume to 0 caused the engine to interpret them as 100.
Fixed crash bug during pitch manipulation
Adjusted log content for bug diagnosis

2025/04/06
[Added]
- Note parameter editing feature
- Copy & paste functionality using the clipboard
- Note deletion feature
- Envelope editing feature
- Pitch editing feature
- Undo/redo functionality
- Note creation feature
- Project tempo and flag editing feature
- UST save functionality
- Vibrato editing feature

[Fixed]
- Fixed bug where vibrato rendering was inverted vertically
- Fixed bug where crossfade did not work correctly when lyrics were changed via batch processing
- Fixed bug where the voicebank would not sing correctly if the ZIP root path was an empty string
- Changed location of the UST load button following addition of UST save functionality

2025/03/26
Notes can now be moved. After selecting a note, please hold your finger on the screen for about one second.

2025/03/25
Added range selection functionality

2025/03/24
Fixed the issue where character encoding selection was not available on the voice bank information screen.
Fixed the issue where icons and sample audio could not be loaded if they were not in the same directory as character.txt.
Fixed the issue where noise occurred during crossfade.
Added note selection functionality (toggle).

2025/03/23
Fixed an issue where UTA fails to process voice banks with filenames containing specific characters.
Fixed an issue that caused immediate audio distortion.
Enhanced logging functionality for improved troubleshooting in future updates.

2025/03/22
VoiceBanks that were not UTA'd properly can now be UTA'd normally. (in cases where the overlap is a negative number, when the wav file is in the original sound root, when no alias is set in oto, or when frq is missing)
ust that could not be loaded normally can now be loaded. (in cases where pitch-related parameters are inconsistent)
Adjusted the layout of the log display screen

2025/03/21
Release