On Wednesday, Mr. Dylan’s website, bobdylan.com, posted what appears to be the cover of the singer’s forthcoming album, “Shadows in the Night,” as well as a single track – a gently sung cover of “Full Moon and Empty Arms,” in an ensemble dominated by a country-tinged steel guitar part. The song, written in 1945 by Buddy Kaye and Ted Mossman, is based on a theme from the third movement of Rachmaninoff’s Piano Concerto No. 2, and was a hit for Frank Sinatra in 1946. Maybe Dylan's next album will be a collection of American Songbook standards, like recent albums by Paul McCartney and Rod Stewart. Like everything about Bob Dylan - it's enigmatic.