Add test tone for testing output device

Hi! I spend a lot of time "negotiating" my various output devices in order to use my Digital Audio Workstation (Ableton Live) of choice and composition software of choice (that's you!) at the same time. While the basic options to choose the output device are there, and there's even the handy feature to restart devices, I wish there was an option for a test tone or test "note" or something equivalent to Ableton's test tone. This way I could directly assess if I chose a valid output device without having to close preferences, pull up music, cross my fingers, and press play. Let me know what you think! Again, really grateful for this awesome Open-Source project and the others like it.