Flux is the only constant in life, and, in San Francisco, for better or worse, change sweeps aside familiar settings with merciless efficiency. There are few better antidotes for vertiginous disruption than a pulse-quickening riff, a seductive melody or a buzz-inducing groove. Above and beyond the essential role musicians play in making civilization civilized, they stand athwart capitalism’s churning creative destruction, providing an oasis of sonic succor. Each night, all around the city, musicians gather for weekly residencies in clubs, bars, restaurants and lounges, establishing a beachhead in the eternal struggle against alienation and entropy. However, regular gigs don’t tend to get much attention. The glitzy one-offs, the concerts featuring a touring act plugged into the ravenous corporate music biz, grab the limelight.