Oakland-based indie rockers Felsen are performing a free concert at Jethro's on Saturday as part of their Left Coast Values Tour.Felsen will be performing tunes from their most recent album, "Breaking Up With Loneliness." Frontman Andrew Griffin started Felsen after his 2006 cancer diagnosis. Less than five months after his diagnosis, Griffin's first and only child was born. As he balanced the responsibilities of fatherhood with ongoing cancer treatment, Griffin turned to songwriting as a coping strategy, which led to the release of Felsen's first album, "Accidental Drowning" in 2009. "Felsen Loves You," an EP on the Ninth Street Opus …