This is the description taken from the Youtube video's page.
In this video there are two Yamaha TX7's and two OPL3 synthesizers. No audio effects were used in the mix. The song is clouds.mid which is from a Windows 95 easter egg (a hidden feature). One laptop is running a midi sequencer with the Voyetra super sapi patch set (drums, crystal patch). The other laptop is running the Symphonix FM Editor with a custom patch bank (bass). Everything else is done with the TX7's.