Bard Hero XIV

Bard Hero XIV adds a rhythm game interface to Final Fantasy XIV's bard performance mode.

It's compatible with most Bard Music Player midi files, although results may vary as they are not designed to be played by hand. To make your own songs for Bard Hero XIV, it's as easy as making a Bard Music Player midi with less notes!

You may need to adjust your in-game UI scale to make the keys line up with the overlay's lines.
Enable "Assign All Notes to Keyboard" in your Bard performance mode settings and assign all the keys.
Run FFXIV in Borderless Windowed mode.
Enter bard's performance mode before starting Bard Hero XIV.
After loading a file, click back into your FFXIV window.
Bard Hero XIV will close itself when the song is over. Reopen it to use it again.
Bard Hero XIV is entirely non-invasive, it does not touch your FFXIV installation/files at all. It is an application overlayed on top of your game, not a mod.