From Zappa’s magnificent and gleefully obscene 1979 album “Sheik Yerbouti” comes “Flakes,” an anthem about unreliable repair technicians and the people that hire them. The Bob Dylan impression and the reference to “frosting a cake with a paper knife” are especially nice touches. “Flakes” is an unusually clean (though not that clean) track from “Sheik,” apparently Zappa’s best-selling album of all time. “Sheik” is also arguably the least politically correct and filthiest album to hit the Billboard Top 25 album chart until the ascendency of gangsta rap. That’s a compliment, by the way.