The Jazz Messengers were the quintessential outfit of the hard-bop era, but as a finishing school for young jazz musicians on their way to illustrious careers, the band had no fixed membership. One historic formation that existed only briefly (in 1959, jazz’s banner year) put the tenor saxophonist Hank Mobley alongside the trumpeter Lee Morgan on the band’s front line. No studio album has been released featuring this particular crew but enough material was recorded for one, at a session 61 years ago this month. That music will see the light of day in April, when Blue Note releases “Just Coolin’,” featuring six tracks from that session. They include two tunes that had never been released in any form — including “Quick Trick,” a sauntering ditty composed by the pianist Bobby Timmons (the author of “Moanin’,” the Messengers’ de facto theme song). Both Morgan and Mobley get brief star turns, the younger trumpeter blasting away first and the saxophonist rising to match his energy. GIOVANNI RUSSONELLO

Aruán Ortíz, ‘Inside Rhythmic Falls, Part II (Echoes)’