Chances are you’ve passed the Rainbow dozens of times and never noticed it. Perched next to the Blue Moon in that nether region between the U District and Wallingford, this dimly lit jazz, rock, and blues joint has long remained a player in Seattle’s mercurial club scene. Some of the country’s finest experimental musicians have stopped in, including Nels Cline and Wayne Horvitz, recalling the space’s old incarnation as the Fabulous Rainbow, a launching pad for locals such as Soundgarden and a late-night place to jam for important out-of-towners. With liquor, burger-type “cuisine,” a pool table, and darts, the Rainbow’s got all the usual bar stuff, but the focus is solidly on the seven-nights-a-week music menu. 722 N.E. 45th St., 206-634-1761.