The studio debut of what’s now known as Miles Davis’ Second Great Quintet came at the end of a two-year stretch during which he already had the rhythm section he wanted (pianist Herbie Hancock, bassist Ron Carter, and drummer Tony Williams), but couldn’t find the right saxophonist. He tried George Coleman, who was too staid and traditional, and Sam Rivers, who was too avant-garde, before bringing in Wayne Shorter. (If you want to hear the early versions of the band, check out the live albums In Europe, My Funny Valentine and Four & More, all of which feature Coleman, and Miles In Tokyo, with Rivers.) Davis was significantly older than his bandmates, especially Williams — the drummer was 17 when he signed on in 1963.

Most of the music on E.S.P. was written by Wayne Shorter or Ron Carter, with Davis contributing “Agitation” and co-writing “Eighty-One” and “Mood” with the bassist. Herbie Hancock brought his piece “Little One,” which he’d re-record for his own Maiden Voyage album on Blue Note a few weeks after these sessions. The group sound is still coming together; you can hear the ways they’re going to move far beyond conventional hard bop, into realms of greater and greater abstraction (particularly live), but there’s still plenty of melody and predictable swing to the rhythm. What’s most obvious, when listening to this music, is how carefully all five of these guys are listening to each other, and challenging each other, at all times. There’s not a moment where they coast, or settle into rote patterns that any other group could have played. Because of that, no matter how pretty the music gets, there’s an underlying tension that never goes away, and which is present throughout all five of this band’s albums.