The Nagisa Music Festival, taking place in Tokyo on April 7-8 and in Osaka on April 29, is one of the most interesting success stories to emerge from the Tokyo dance party scene.

Held biannually and with acts on the bill this year including Derrick May, Takkyu Ishino, System7 and Hallucinogen, the festival first took place in 2003, out of the rubble of the local dance music scene's worst year ever: Venue changes and event cancellations due to a lack of permits were all too common and the backlash affected events held in Japan like Solstice Music Festival, The Gathering and incidentally, Harukaze, the Yoyogi Park day-raves that Nagisa has handily replaced.

The masterminds behind Nagisa are three brilliant producers who decided to pool their monster networks of resources together: Takashi Ishihara, who founded a one-stop Web site for clubbers, clubberia.com; Masaru Morita of visuals company M.M. Delight; and "Nanbei" Suzuki, of green promoters Earth Garden, set out to make something different that would still fit within the strict requirements of the system (literally in the case of Odaiba, because the event takes place inside a fence).

The result is a constantly evolving, open-air festival that features music from house, techno, trance, reggae, jam-band music, rock and ambient genres.

It's also Earth friendly. This year, the electricity for all the stages at Nagisa will be generated by bio-diesel, created by refined secondhand vegetable oil. Past years have even seen success in attempts to run the whole show on solar power.

Nagisa means "beach," but Odaiba Open Court, which faces the impressive Fuji Television building on the man-made island, has become the party's home. Open Court is more of a concrete desert than a beach, but it has the space to set up seven stages and all the room to feed, quench and relieve large crowds of ravenous young people.

Headlining Nagisa this year in Tokyo are progressive-rock veterans System7 (Saturday), and Detroit-techno originator Derrick May and psychedelic trance pioneer Hallucinogen (both Sunday). DJ Takkyu Ishino headlines in Osaka.

System7, comprised of Steve Hillage and Miquette Giraudy, have played in Japan every year since 1999. The duo have released more than six albums since forming in the 1990s.

Derrick May hasn't released a track since 1992, taking a hard stand against the record industry, but his popularity as a DJ only seems to get stronger. (May also performs at Air in Daikanyama on April 14, 10 p.m. start).

Down at the very base of the psychedelic-trance family tree is Hallucinogen's Simon Posford, whose 1995 album "Twisted" is viewed by many as the start of the psy-trance genre. More of a Merlin figure than a hands-on father type, Posford's influence can still be felt on much of psy-trance today. He is making his first appearance at Nagisa.

Other artists performing represent the heart of Japan's dance scene crop: Masa and Ree. K of Space Gathering, Ta-Ka of Mother Records Japan, Ryo of Solstice Music, Miki from Sirius Records and a host of others.

The festival takes place April 7 (1 to 8 p.m.) and 8 (9 a.m. to 8 p.m.) at Odaiba Open Court in Koto Ward and April 29 at Osaka Maishima Sports Island. Day tickets are 4,000 yen (Tokyo) and 3,000 yen (Osaka). For directions and the complete lineup, visit www.nagisamusicfestival.jp/ or call (03) 5410-1470.