Kobold Choir

You can click on the Kobolds to make them sing, or press buttons on your keyboard to play the associated note.
To see keyboard bindings toggle the keyboard display.
Right clicking a kobold results in the kobold singing an octave higher.

Holding Shift while pressing a button or cliking a kobold will make the kobold sing one octave higher.
Holding Ctrl or Alt will make the kobold sing one octave lower.

You can also make them sing a full song by selecting one on the drop down above and clicking the play button.
You can upload MIDI files (or type a MIDI URL) and the kobolds will sing that.
If you want to find MIDI files to play, BitMidi is a good place for it.