The Southern California band Quetzal recently celebrated its 20th anniversary with a blowout concert that seemed to attract as many musicians as regular people. The band has maintained such a strong presence in the SoCal Chicano music scene that its members could be considered padrinos and padrinas of that free-flowing musical is respected and admired as much for its commitment to social justice, activism and education — lead singer Martha Gonzalez has a Ph.D — as for its folk-infused music, which gets a marvelous showcase in this Tiny Desk Concert. While the instrumentation is stripped down, the sound is full; the music penetrates the intellect even as it makes your hips group runs a tight ship musically: Gonzalez’s voice could be heard well past the confines of the Tiny Desk, all the way to our web-designing neighbors; guitarist Quetzal Flores unplugged and worked the Mexican jarana for both rhythm and melody, often at the same time; violinist Rocio Marron wove blues licks into Me