Steve raises a very good point.
Up until, I'd say, the early 90s a wide variety of styles constituted Northern Soul. At that point I think there was a concerted effort on the part of the few 'newies' jocks left to get back to basics and try to programme predominently 60s uptempo soul records with a straightforward 4/4 beat. But the great clubs of the classic era, from the Wheel through the Torch, Mecca, Wigan, Cleethorpes and Stafford all found room for off-the-wall dance music of many different flavours.
If you were to pick a record which summed up the sound of each of these clubs someone else could equally pick something completely and utterly different: Don Garner's Cheating Kind was a Mecca record, but so was Snoopy Dean. Chrysler & The Monarchs was a Stafford record, but equally Mel Stewart "No Work No Pay No Eat" was too (I dug this out the other day: would never get played anywhere now, I guess, but still sounds interesting. Rare too, not that it should matter.)
Levine maintains that Northern Soul was always a specific generic style of music (4/4 rhythm, soaring strings, predictable harmonic structure, 'lifestlye' lyrics) a revisionist manifesto to fit in with the kind of music he makes now. Such revisionism is completely ludicrous.