LAGGG in multiplayer

[Ryuukumori]

i have a home network here, and i play multiplayer against a friend. It works great except one bug i found ruined it. sometimes, not always, the other play starts the song a bit earlier than the other, thus makes it hard to hear your own computer's sound of the song. it also ruins the score if one plays a bit longer than the other. whats up? i think its lag between the server or something...