President Obama has flexed his larynx yet again, this time singing a few lines of Robert Johnson‘s “Sweet Home Chicago” during a concert at the White House yesterday. We first heard the President sing Al Green’s “Let’s Stay Together” at a fundraiser last month, and admittedly, the snippet of Obama’s vocal ability left us, and apparently even American Idol, hankering for more. So when he was baited by Buddy Guy (who was part of an All Star Band including B.B. King, Booker T. Jones, Mick Jagger and Derek Trucks), who said “I heard you had sung Al Green, so you started something so you gotta keep it up!” Obama, although reluctant at first, had little choice but to belt out a few lines from “Sweet Home Chicago”. Look out for the pretty amazing moment when Obama holds the microphone out to B.B. King, and the two have a brief back-and-forth style sing-a-long.