In my humble opinion Crossover is the bastard child of Northern & Modern Soul - roughly speaking between the years of '68 - '73, although I would argue personally that it extends a little further into the 7ts than that. It was a period in time when production tequniques were improving, from the raw 6ts sound recordings on 4 track, but before they had become too sophisticated with the dawn of the Philly Sound & Disco.
Like most things, there is an overlap & it is as much about a 'sound' as it is a period in time, thing is, you have to have the ear to recognise it, some of the weird explanations on this thread are frankly laughable, possibly because they are coming from folk who are actually more into Northern Soul, nothing wrong with that, but you cannot listen to Crossover from a purely NS perspective. There are many, many records that the NS Scene have adopted from the Crossover Scene & jolly good that is too & Im all for it, but a lot of these records prior to the 8ts (stand fast the last hour at the Mecca ?), would never have been considered NS in the traditional sense.
I liken the explanation & understanding of Crossover as a genre of the British Soul Scene, to explaining Northern Soul to someone who knows what soul music is, but has no real idea what NS is, I hope that explanation will help some on the NS Scene to 'get' how difficult & frustarating that can be.
To be fair, Ivor, Dave, Sean & Steve to name but four, have done a great job, but some of the totally off the mark explanations & examples of Crossover on here are plain mumbo jumbo & have no bearing what so ever on Crossover, no wonder people get confused.
Russ x