Recorded at Ardent Studios in Memphis, Hot Buttered Soul was as revolutionary for soul music as anything by James Brown, Sly Stone or George Clinton. Although in-house Stax writer Hayes had recorded as solo artist before, this, his second album, reshaped the notion of what could be done with the long-playing format in a genre dominated by the three-minute single.
With its four tracks, Hayes extended his songs and created something completely new. Working with producer Al Bell and members of the Bar-Kays as his backing band, Hot Buttered Soul's long instrumental passages simply revelled in their repetition.
It starts with a 12-minute version of Bacharach and David's standard, Walk on By. Its sultry setting still sounds contemporary; a huge horn fanfare; fuzz guitar, subtly introduced vocals. When Hayes's Hammond begins to dominate in its tenth minute, you are mesmerised by the groove.
With the statement, "I'm talking about the power of love now, I'm telling you what love can do" at the start of Jimmy Webb's By the Time I Get to Phoenix, Hayes single-handedly launched the 'love man' genre that was soon to prevail; the roots of Barry White's sensual symphonies and Marvin Gaye's Let's Get It On can be traced right back to here.
Hayes strips Webb's narrative down to its bare bones, spelling out the tale through his extended rap. His level of detail is breathtaking. He outlines what car the protagonist is driving, the songs that the couple would have sung between them. It's eight-and-a-half minutes (and there's still another ten to go!) before it finally breaks into the melody.
Of the album's remaining 50%, the space and controlled aggression of the Hayes-penned Hyperbolicsyllabicsesquedalymistic moves from deep soul to something approaching krautrock. It is only the relatively conventional One Woman that makes you remember you are listening to what is, nominally, an R&B record.
With a picture of Hayes' bald head on the cover, Hot Buttered Soul really is one of the landmark soul albums. A huge commercial and critical success, it brought Hayes forever out of the backroom. Twenty years after its release, its languorous sound was still influencing; this time being sampled extensively for hip hop. Forty years on, it sounds as curiously charming and unsettling as ever.