Since Kacey Musgraves won all those Grammys, some of the younger or previously less explorative fans who adopted her as their first favorite country star have looked to Nashville and asked: “Got any more where this one came from?” After some hemming and hawing, since that cupboard isn’t exactly jam-packed, the answer might emerge: “Actually, yes.” Because Brandy Clark is the necessary next stop for anyone joining this program already in progress and finding that Music City is the richest source