This is a small EXE written in Visual Basic 6 that plays all open UTAU windows like the commonly available UTAU plugin is supposed to do for playing multi-track vocals in sync. I made this because the UTAU plugin doesn't work on non-Japanese locale systems (like mine). I also decided to make it a standard Windows app instead of a plugin because I find it more convenient to have a small window with start & stop buttons off to the side instead of having to navigate one of the UTAU menus every time I want to play all the windows.
This app works by sending the WPARAM command message "92" to all windows on your desktop that have the string "UTAU" in their title. UTAU was written to process external command messages passed from Windows; decimal 92 fires the UTAU "replay" command. So you need to have already rendered (played) all your open UTAU windows already before clicking the "Start" button in this app. Simply firing the UTAU "play" command wouldn't work as well because all the windows would be rendered by multiple instances of the resampler before playing, & I found that those multiple instances don't always finish at the same time so the playback of all the windows would be out of sync.