When a man puts his arm around a woman's arm and begins to Jack himself Off while the women fingers herself. its helps by keeping both on beat. Can also Become a Triplet if its 2 Girls and a guy in the middle.
Jon: Hey man last night i had a Duet
Jon: but not just any kind
Bill: what kind is it?
Jon: A Dutch Duet!!!
Bill: No Way!!! can i try
Jon: if i do it with you than it will be a Quearet.
Jon: you Homo