For Japan's trance music fans, this weekend is the last big outdoor romp of summer.

Tens of thousands of people will spend Saturday, Sunday and into Respect for the Aged Day on Monday stomping to this form of electronic dance music, with its thumping basslines, anthemic melodies and emotional riffs, at one of at least a dozen open-air events across Japan.

Progressive trance organizer Mind Games' Labyrinth 2006 ( www.mindgames.jp/ ) in Gunma Prefecture has already sold all of its 1,300 advance-only tickets. The more tribal Earth Energy event by Earthcore Japan and Psy16 ( www.psy16.com/ ) in Yamanashi Prefecture is inspired by, but not yet associated with, the global "Earthdance 2006" movement being staged this weekend at 250 events in 50 countries.