It seems slightly redundant to be recommending one of best-selling jazz albums in history to anyone, but the remarkable thing about The Köln Concert is how almost 50 years of ubiquity has done nothing to dim the audacity and subversive genius of it. The troubled, seat-of-the-pants backstory behind Keith Jarrett’s 1975 performance at the Cologne Opera House has become something of a legend, but it also serves to highlight the almost punk attitude of Jarrett sitting down at a piano — an out of tune and out of condition one at that — and pouring out one of the greatest pieces of improvisation ever committed to tape. Sometimes vamping on just one or two chords, Jarrett summons almost the entire spectrum of music, from jazz to classical, ragtime to blues, funk to avant-garde and more, and every single bar contains a new multitudes of melodic riches and sophistication. Jarrett’s joy at having such possibilities at his fingertips is audible (literally so when you can hear him whooping along). It’s no wonder that generation after generation of casual jazz listeners, prog fans, stoners, post clubbers, hip-hop samplers and more still keep find themselves drawn in.