Gramophone readers will forever associate Julius Eastman with Peter Maxwell Davies’s own 1970 recording of Eight Songs for a Mad King, where Eastman’s gravelly voice, all dark and brooding, created a definitive interpretation of George III’s descent into the abyss. Readers elsewhere will more likely namecheck Eastman as the keyboard player in disco outfit Dinosaur L; and, had you lived in New York City during the 1970s, you might have encountered Eastman playing jazz piano in his bassist brother Gerry Eastman’s band or performing as a singer-for-hire in Baroque oratorios – or unpicking new compositions under the batons of Pierre Boulez, Lukas Foss or Zubin Mehta.

But all this frenzied activity was, you feel, something he did to pass the time when he wasn’t composing. Eastman’s own music might at first feel allied to the early minimalism of Riley, Glass or Reich. But Eastman was black, gay and proud in a new-music scene that was overwhelmingly white; and, as much as he was fascinated by minimalism and by Cage and Feldman, whose music he performed regularly, his cultural antennae pointed elsewhere. His raison d’être for establishing melodic loops was to torpedo their progress through improvisation.

Femenine – written in 1974 and performed that year by Petr Kotik’s SEM Ensemble with Eastman on piano – is a typical Eastman construct. His notation fused the approach Terry Riley had pioneered with In C – musicians working through a sequence of melodic fragments – with what jazz musicians would term a ‘lead sheet’: a melodic skeleton around which to improvise. The score is available online for free download; but connecting this ornate 72 minute performance, rendered by a mixed ensemble of wind, strings and percussion, with that sketchy five-page short score, much of it on one or two staves, might require a leap of faith.

A stark, syncopated riff for vibraphone moves against interrupting slabs of harmony and flare-ups of melodic gossip for other unspecified instruments. Indications written into the score such as ‘displace by one 16th note’ might drop hints about what will follow, but nothing can prepare you for the ecstatic ritual as it actually unfolds. Mechanically shaken sleigh bells, a gizmo of Eastman’s own invention, provide a failsafe pulse – and, a groove now rolling, he acts as a bandleader in the Duke Ellington mould, cajoling and shaping a performance from behind the keyboard.

With the vibraphone setting the mood, Eastman initially holds back before gradually asserting himself, bolstering the basic harmonies but then extending the harmony beyond itself – flooding the senses with churchy harmonies or focusing in on one other instrumental line, teasing it out of phase with a cavorting boogie-woogie line. There’s a moment of sheer magic, around 48 minutes in, as fresh harmonic material begins to glow from inside the ensemble. Now orgiastic joy and snarling defiance coexist – which is exactly how Eastman liked it.