ELTON JOHN/LEON RUSSELL The Union [Decca Records] This much-anticipated collaboration between Elton John and Leon Russell had all the ingredients for greatness—two brilliant singers and pianists, an extraordinary producer in T Bone Burnett, and a profound mutual admiration between the artists involved. It turns out that “greatness” is too strong a word, but the album does have its rewards. As you might expect, The Union mixes Russell’s bluesy,...