San Francisco One minute, Bruce and Medea Bern were laughing at the jokes of celebrity chef Hugh Acheson as he whipped up a shrimp soup. The next, they were swaying to the psychedelic soul sounds of the Monophonics.

“Every time we come here there’s something different,” Ms. Bern, a 59-year-old writer from San Mateo, Calif., said Saturday of the Outside Lands Music and Arts Festival here.

The...