After celebrated duets with Lady Gaga and others, Tony Bennett finds a deep affinity with jazz improviser and songbook veteran Diana Krall on this set of Gershwin classics. Not since Rosemary Clooney has a Bennett partner demonstrated such respect for lyric and melody, or so much lively spontaneity. Krall’s smooth, urbane tone complements Bennett’s clipped, streetwise charisma, most effectively on “Fascinating Rhythm” and "I’ve Got a Crush on You,” while “Do It Again” sinks into coyness.