Tucked within the enormous Blue Note catalog is a whole subfolder unto itself: recording after classic recording by Art Blakey & The Jazz Messengers. With the release of the long-lost Just Coolin’, it becomes clear that the Messengers’ discography is even more extensive than previously known. Because this particular incarnation of the Messengers—with Hank Mobley on tenor sax, Lee Morgan on trumpet, Bobby Timmons on piano, and Jymie Merritt on bass—recorded the live, two-volume At the Jazz Corner of the World at Birdland a mere few weeks after Just Coolin’, the latter likely got shelved as superfluous. There were four repeat tunes (Mobley’s title track, “M&M,” and “Hipsippy Blues” plus the standard “Close Your Eyes”), and fair enough, the live versions packed greater excitement, with a satisfyingly raw sound. But these unearthed studio takes still compel attention, adding to the historical record and our knowledge of each of these legendary players. Two previously unknown numbers, Bobby Timmons’ “Quick Trick” and the unattributed “Jimerick,” are also worthy additions to the Messengers’ compositional library, which spans more than four decades. The Morgan-Timmons-Merritt core of this Messengers lineup was remarkably potent and long-lived: Just before Mobley, Benny Golson was in the front line for the classic Moanin’, and just after Mobley, Wayne Shorter joined for The Big Beat, The Freedom Rider, and other essentials. Just Coolin’ provides another look at a transitional lineup with an appeal of its own.