Celebrate Play Music On the Porch Day (it’s always the last Sat. in Aug.), Aug. 27 bluegrass birthdays, and a roots-rich mixed salad o’ sounds when Mark Humphrey hosts Roots Music & Beyond this Sat. He’ll be joined on air by other RM&B hosts to urge listeners to support KPFK, and we’ve got some terrific `thank you’ gifts for those who do, including the 7-CD set John Prine—Crooked Piece of Time: The Complete Atlantic/Asylum Recordings (1971-1980). Roots Music & Beyond airs Saturdays 7-9 a.m. PST on KPFK, 90.7 FM, Los Angeles and streams `live’ worldwide. If you miss the `live’ broadcast you still have two weeks to hear the show at the station’s Audio Archives.