Mixwaver II is a great "mixing" game. It's a one-game-only emulator for the Beatmania arcade game. It works well on a 6-button layout too.
If you google search for mixwaver, you should find a site that says it's the official release site... it might be mostly in japanese or korean though. My friend gave me the installer file when I installed it, so I don't know precisely which one he downloaded... but the game is in English, so I can play it just fine, just can't read its web page.

I can probably email you the installer file if you want. Songs are another matter - he brought over his song collection on two CDs. Those might be a trick to find.