Shoutbox

There is another way to hear music together.
U simply starts a audio conversation and set the output audio as ur input one.
Go to volume control --> properties --> record --> stereo mixer
(translated to English, so sorry if it isn't the exact words) and choose it,
now tick the option box below it (after pressing ok in the properties).
Start the audio conversation, he should hear what u hear (i.e. the music, and some other sounds if there are ).