DETROIT -- The pairing of Daryl Hall & John Oates and Train on Sunday night, May 20, at Little Caesars Arena had the potential to be a one-plus-one equals more than two proposition.It didn't quite add up that way, unfortunately. What was billed pre-tour to be a genuine co-headline outing, with each act playing an hour followed by a half-hour combined finale, turned into a more standard affair with Hall & Oates as the clear headliner and Train frontman Pat Monahan joining the duo for three songs.