I'd argue with you and
@blissblogger about this due to my interaction with Twisted Wheel veterans
what happened was speed freaks in Manchester in the late 60s needed fast paced tunes to keep the buzz going but what happened was the record companies stopped making those tunes ( and that includes Motown, they went psychedelic with the temptations. etc ) so some people started dropping acid and grew their hair but some still wanted to jack up speed and dance the night away so they had to find "more of the same" but no one was making it so they had to settle for second tier shit from the past
no one was making Motown hits in 1971, least of all Motown
before it was called Northern Soul (a term made up by a record shop owner / music journalist down South) it was known as rare soul. Rare necessarily means not many copies in the world - and if there aren't many copies in the world that's because it never sold enough that there would be represses.
The rarer the better so that meant singles that had only reached the sort of promo stage, a few 100 copies sent out to radio stations and such like.
The lore of how far people would go to get rare soul is rich - there's this story of how Ian Levine, on holiday with his rich parents in Florida, took the bus every day for five hours or something like that to this out of the way warehouse full of remaindered copies of singles, a treasure trove of flops, and he spent the whole day each day of this vacation digging his way through all this crap, finding maybe 100 singles no one knew about, that then became the basis of his deejaying renown.
Yeah no one was making that kind of music by 1970 - black music had gotten slower, funkier, groovier. But there was a huge swathe of commercially successful stuff in that uptempo urban soul style from the recent past - early-mid 1960s - and Northern Soul deejays and fans zealously avoided it.
They also shunned the brisker tempo, lushly produced Philly sound, which in some ways was a Motown-redux, on the grounds that it was commercial.
It's the archetype of an obscurantist scene, right down to the thing of deejays whiting out the labels - or even putting fake labels - on the singles so that rival deejays couldn't find out the name of the artist / song. You got similar practice popping up independently in the obscure rockabilly fetish scene. It's like a sort of retro version of the dubplate - I alone have this tune, if you want to hear it you must come see me deejaying .