Man, I wrote this detailed thing and inadvertently wiped it. I agree that spiritual jazz and soul jazz are different. Spiritual jazz typically claims to be rooted in A Love Supreme, as @frogman noted, but the sounds can be very different- the concept of "transcendence" through music is a common denominator, but that’s true of a lot of music. Alice Coltrane did some amazing records before she left for the ashram. This track, on Ptah, the El Daoud, is worth the price of admission: https://www.youtube.com/watch?v=QUMuDWDVd20
The record was out of print since 1974 and finally got reissued from a digital master in the last couple years.
The goldmine, as I learned from a fellow collector, was probably the Strata-East label, a small collective. Cecil McBee, probably one of the most tuneful bassists, is on some of the records, but there are great ones and clunkers- the catalog has been reviewed a number of times.
Interestingly, the Grubbs brothers out of Philly, who had a group called The Visitors, and did what is considered archetypal "soul jazz" were related to Coltrane’s first wife. Bobby Hamilton’s Dream Queen is sort of a slo-fi lounge act, but it became a cult record commanding high prices. The title track is a killer. It was reissued from the tape, cut by the notorious Bernie G. and should cost you 30 bucks, rather than 4 figures for an OG. That was a private label release, as were many others in the spiritual jazz vein. Milt Ward and Virgo Spectrum-- reissued but from a needle drop. An OG is hard to find and probably pretty pricey now. Jothan Callins, an educator out of Birmingham, Alabama who studied with Nathan Davis at Pitt and played with Sun Ra’s orchestra did a one and done as a featured artist called Winds of Change. I do not know if that was reissued on vinyl. Finding the masters is very difficult for these small pressings.
Pharoah’s self-titled, on the India Navigation label, is another rarity and commands big money. It was reissued, pulled from a digital file. Harvest Time is the track. It’s very meditative, and doesn’t have his signature aggressive squawk.
Other small labels- check Nimbus West, Horace Tapscott; Tribe in Detroit, Black Jazz, a label funded by Dick Schory, famous for some of the percussion spectaculars like Bang, Barroom, is more soul and funk.
I’ve written about a number of these, but there’s lots of info on the web. I’d say just dig in and listen. Almost anything that Cecil McBee plays on is good, even if it is straight jazz, blues or more esoteric stuff- listen to his work on Art Pepper’s late recording of Patricia-https://www.youtube.com/watch?v=zXNpG0w_rks
It’s Art, Cecil, Roy Haynes and Stanley Cowell on piano- Cowell co-founded Strata East. There’s also new work being released in both genres. There’s an English collective called Maisha that worked with Gary Bartz, one of the original sidemen from the period. The record was cut direct to disc and isn’t terribly expensive. Part of the fun is exploration. These guys were cutting new ground at the time- a lot of it due to the recession in mainstream jazz, the emergence of black power and focus on the local community, as well as the entry of Eastern influences. You can hear this in Abdul Wadud’s By Myself, a classically trained musician who was also into free jazz. That album was reissued a few years ago-- another rarity that is now accessible for a modest price. You’ll find some stuff that resonates and other stuff that is perhaps a little too out there. But, it will also expand your listening horizons: some stuff I would have regarded as cacophony is now readily digestible.