I made a program for people to sing together over the Internet. It works bucket brigade style, where each person in the brigade is three seconds behind the person in front of them. Everyone can hear everyone before then, and be heard by everyone after them. It runs in the browser, though currently it only works in Chrome. It also works best if you have wired headphones, so it doesn't mix your sound with other people's. Would anyone be interested in trying it out? Jeff