Released in the mid-’70s, Gong’s “Radio Gnome Invisible” trilogy—Flying Teapot, Angel’s Egg, and You—established the musical vocabulary used by neo-spacers such as Ozric Tentacles. At once muscular and loose-jointed (in more ways than one), Gong was serious about not being serious. Four members of the classic lineup—glissando-happy guitarist Daevid Allen, saxist Didier Malherbe, bassist Mike Howlett, and Gilli Smyth (“space whispers”)—are bringing their “floating anarchy” to the U.S. for the first time as a unit, joined by drummer Pip Pyle (Hatfield and the North) and mysterious guitarist Steffi Sharpstrings. At 8 p.m. at the Birchmere, 3901 Mount Vernon Ave., Alexandria. $20. (703) 549-5919.CP