Bluegrass feel, sweetly sung: Mostly Marys is an acoustic crowd-pleasing East Bay quartet that plays bluegrass, old-time music, and whatever else fits. Together since 2017, they combine rich harmonies with fiddle, guitar, banjo, blues harp, and bass. Mostly Marys have an infectious enthusiasm for bringing joy to their audience with a repertoire that includes traditional tunes as well as modern troubadours: Hazel Dickens and John Prine; Bill Monroe and Patti Griffin; Ola Belle Reed and Townes Van Zandt — and now we’re adding original songs to the mix. At times the listener is blissfully drawn in while at other times foot stomping and dancing can’t be helped.