Not many small groups were working harder in the late 1950s, to greater acclaim, than Art Blakey & The Jazz Messengers.

But when we talk about The Jazz Messengers in that period, we’re often referring to the unstoppable crew heard on Moanin’. With the exception of Blakey, who led from the drum chair, that was an all-Philadelphia band assembled by tenor saxophonist and composer Benny Golson; it had a fierce young Lee Morgan on trumpet, along with Jymie Merritt on bass and Bobby Timmons, who composed the album’s title track, on piano.

Moanin’ came out in 1959, but it had been recorded the previous fall. By the time of its release, Golson had decamped to form The Jazztet with trumpeter Art Farmer. The Jazz Messengers would soon regroup with another legendary edition, featuring Newark-born tenor saxophonist and composer Wayne Shorter; for the next several years, the electrifying Morgan-and-Shorter front line would define the sound of the band.

But as any hard-bop scholar will tell you, there was a transitional version of Blakey’s band in ’59, one that put Hank Mobley — a charter member of The Jazz Messengers — back in rotation on tenor saxophone. This was the group that convened at Rudy Van Gelder’s home studio in Hackensack, N.J. on March 8, to record a studio album.

That album, Just Coolin’, will soon be released for the first time, more than 60 years after it was made. Blue Note announced an April 24 release date this morning, and shared the first single: “Quick Trick,” a sauntering shuffle composed by Timmons, and never before issued in any form.

Jazz discographers have long known about the March 8 session, and I’ve seen talk of some bootleg recordings in circulation. But for the vast majority of listeners, Just Coolin’ will be a fresh discovery — even though its personnel and track list invite close comparison with a contemporaneous live date recorded on April 15, and released in two volumes as At the Jazz Corner of the World.

“Blue Note had enjoyed great success with multi-volume location recordings, an approach that began with A Night at Birdland with the Art Blakey Quintet in 1954 and The Jazz Messengers at the Café Bohemia in 1955,” explains Bob Blumenthal in liner notes for Just Coolin’.

“The label may also have been cognizant of the live European recordings that were already appearing with extended versions of the band’s previously recorded hits,” he adds. “In any event, the resulting Birdland tracks included four of the six titles recorded in March and consigned the present performances to the vaults.”

The undeniable spark of At the Jazz Corner of the World goes a long way toward explaining this decision. Though it was only recorded five weeks later, the band sounds surer in its swagger; “Hipsippy Blues,” a Mobley tune that opens both releases, begins at a slower tempo on the live version, producing a sense of heavier traction. (Eventually the pace does quicken, as a function of excitement.) Then, too, there’s the priceless banter that Blakey issues from the bandstand, as on the introduction to “Close Your Eyes”:

If you feel like pattin’ your feet, pat your feet. And if you feel like clappin’ your hands, clap your hands. And if you feel like takin’ off your shoes, take off your shoes. We are here to have a ball. So we want you to leave your worldly troubles outside, and come in here and swing, Ladies and Gentlemen.

But there’s reason to be enthusiastic about the release of studio material by this band — and not just because of the chance to hear “Quick Trick” and one more unearthed tune, a scorcher called “Jimerick,” for the first time. (The latter has an unknown provenance; it seems quite possible that its composer was Jymie Merritt.)

Morgan, for one thing, is in bravura form throughout the session, which also includes some primo Timmons. In “Quick Trick,” listen for the presence and power of Blakey’s trademark press rolls during the melody — and the way the horns briefly interject during the piano solo, as if chuckling at an inside joke.

The other big reason, of course, is Mobley, who wrote three of the six tunes on the album: “Hipsippy Blues,” a brighter theme called “M&M,” and the midtempo-swinging title track. There are stronger illustrations of Mobley’s tenor playing elsewhere on record, but his ease in this band is clear.

Mobley would appear with The Jazz Messengers at the Newport Jazz Festival that July, playing a set that began with “M&M.” But his days in the band were numbered. “When Mobley failed to appear at a Canadian jazz festival, Morgan pulled Wayne Shorter out of the Maynard Ferguson big band to take his place and Blakey liked what he heard,” Blumenthal writes.

Still, there was ample chemistry in the short-lived Morgan-and-Mobley edition of the band. This historical document, produced for release by Zev Feldman, substantially adds to our understanding of it.