Many of the best songwriters come in pairs: John Lennon and Paul McCartney; Mick Jagger and Keith Richards; Elton John and Bernie Taupin; Carole King and Gerry Goffin; Robert Plant and Jimmy Page; the Gallagher brothers. The list could go on ad nauseum. Even when some songwriters are perfectly capable on their own, some work better as one half of a duo, repeatedly bouncing ideas off each other like players in an Olympic ping-pong match, achievin…