The city providing the setting and inspiration for tonight’s installment is Nashville. Dave Grohl visits with country legends old and new (represented, respectively, by Dolly Parton and Carrie Underwood). There’s a new song – and on the same night, at the same time in real life, the Foo Fighters also are in Nashville, hosting a sold-out, come-in-costume concert at the famed Ryman Auditorium.