Nancy & Beth - It's the Girl (Megan Mullally on Comedy Bang Bang)
Nancy & Beth are Megan Mullally (Childrens Hospital, Party Down, Will & Grace) and Stephanie Hunt (Friday Night Lights -- she was in Landry's band Crucifictorious).
This is from their live performance on Comedy Bang Bang Ep. 171 - http://www.earwolf.com/episode/scrog-secretions/
"It's the Girl" a song from the 1930s. I couldn't find who originally wrote it, but it was performed in 1931 by the Boswell Sisters (http://youtu.be/62bRDQzN8Xw) and Freddie Rich's Radio Orchestra (http://youtu.be/S1UsdtrcnkE)
Nancy & Beth also performed:
Jack, You're Dead (http://youtu.be/gQVWCnf8gSk)
and
In the Cool of the Day (http://youtu.be/F5aLCfFSnE4)