On the surface, Nellie McKay has always come across as a sweet-cheeked Doris Day fan who plays piano and sings with the nuanced voice of an aged jazz great. Listen for more than a few seconds, however, and you’ll find she’s cooing through lyrics about stalkers and stabbings and misbegotten foreign policy. She also raps. And sometimes she leads audiences through Mandarin-language sing-alongs. Though she paid tribute to Day on 2009’sNormal As Blueberry Pie, she returns to her own material with 2010’s Home Sweet Mobile Home, which shows McKay dabbling in global sounds thanks to artistic guidance from David Byrne.