Every year, 327 cities around the world arrange to simultaneously celebrate the first day of summer. So on Sunday, Make Music New York sponsors 800+ free performances spanning all five boroughs. The most appropriately superlative event is at the Guggenheim, where 80 trombonists will line the museum's spiraling walkway for the east coast premiere of Henry Brant's Orbits.

At the Celebrate Brooklyn Festival, the deranged string quartet Ethel & Gutbucket performs their original score to La Nave de Los Monstruos, an erotic sci-fi movie from 1950's Mexico, in Prospect Park on Saturday. If you prefer classical music with actual class, the Emerson String Quartet plays Schubert at Town Hall on Sunday.

There are two big black metal shows this weekend: Akitsa, Bone Awl, and Ashdautus at Fontana's, and Absu at BB King's. Also, see Amayo's afrobeat Fu-Arkist-Ra for free this Saturday. And Sunday, skank to the sinewy ska of the Aggrolites.

Club kids: Davide Squillace headlines at N. 8th Street; we're told it will "blow your face off." At Studio B, booze up with electro-pop outfit Thunderheist tonight, or wait for Jeff Samuel's brainier techno tomorrow. On Saturday, you'll have to wake up earlier than usual for Juan MacLean's late afternoon DJ set at Webster Hall.

And in jazz, Geri Allen leads Ravi Coltrane and Jeff Watts at Iridium all weekend, while Dave Douglas & Brass Ecstasy channel folk and soul at the Standard. Also, Renee Rosnes plays the Vanguard.