Yeah, I guess the rhythm. Neither song is the greatest either artist ever did. The McCartney/Nirvana song is literally just both of them resting on their laurels and 'jamming,' which any fan of theirs would lap up. At the bottom of "Istanbul" is a pretty basic Boorer chord progression - which was no doubt what Morrissey asked for. Matt Walker's percussion and Morrissey's lyrics are really the only things that save the song.