When looking at any playable instrument, be it in plaza or in a condo, holding c will make an “Instrument Volume Slider” appear in the bottom left (close to the slider for media player volume). I think it’s a little annoying when someone is just mashing keys on a keyboard, or using a macro that causes a lot of notes to be played at once. It’s inconvenient having to go into the audio settings just to change the volume of instruments, then have to go back when I want to change it again later.