HBO’s Boardwalk Empire doesn’t skimp on its sets or on its music. Vince Giordano & The Nighthawks serve as the house band for continuity of sound and style, but the guest vocalists are deliberately varied to the point of being a cross-section of popular music. The National’s Matt Berninger is a natural to handle “I’ll See You in My Dreams,” though he surprises everyone by singing it in a higher key. Patti Smith sounds like she’s having a blast drifting back decades for “I Ain’t Got Nobody.” Elvis Costello, a perennial who’s among the hardest-working men in show business, finds that “It Had to Be You” fits his elder statesmen role. And no one’s a better throwback singer than the former Buster Poindexter himself, David Johansen; he’s perfect for “Strut Miss Lizzie.” Pokey LaFarge is in the right spot for “Lovesick Blues,” as is Liza Minelli in her glory for “You’ve Got to See Mama Ev’ry Night.”