Morphine will release Cocoon, an album of previously unreleased songs recorded in 1998, on Dec. 4. Dana Colley, the band's saxophonist, has added new baritone sax parts to three of its tracks.

The Cambridge, Massachusetts alt-rock trio — whose lead instrumentation consisted of baritone saxophone and a two-string fretless bass — disbanded after vocalist-bassist Mark Sandman died in 1999. Morphine recorded Cocoon's material with producers Paul Q. Kolderie and Sean Slade in sessions that preceded those for their final album, 2000's The Night. When Sandman refocused the band on what became The Night, he abandoned the Cocoon sessions.

Kolderie worked with Sandman's life partner, Sabine Hrechdakian, to transfer and remix the tapes in 2023. The new release presents the songs differently from the versions that circulated on bootlegs and the 2004 compilation Sandbox. It also features never-before-published photographs and liner notes by essayist Hanif Abdurraqib.

The title track, released Thursday, opens with baritone sax dominating a slow-dripping groove that sets up Sandman's opening lines: "Come on in to my cocoon, no one comes in except for you." The song is jazzy and evocative of late nights in smoky clubs. Morphine's trademark sense of space — room for the sax, Sandman's voice, and ear candy like acoustic guitar, echoey cymbals, and distant piano — takes center stage, along with the group's characteristically unhurried melodic sensibility.

The Cocoon sessions found Morphine experimenting with different instrumentation, including piano and drumming from friends and collaborators.

"Mark loved performing and traveling the world, but he also loved to come home and cocoon," Hrechdakian said in a statement. "It was our home and his studio, so there was always music happening, tape running, friends dropping by at all hours, lots of cooking. The lyrics speak to the hardship of being away from loved ones while the band was on tour and the joys of homecoming. There's also this thread of space travel that runs through the album, so I imagine the cocoon as a kind of spaceship for two who leave the world and return to it."

Colley described the experience of returning to the material decades later. "Coming back to these recordings years later was a surreal experience," he said. "It was like having one foot in the past and one in the present, with my saxophone bridging the gap."

Between Morphine's foundation and Sandman's death, the group released four albums, not counting the posthumous The Night. Their 1993 album Cure for Pain became an indie hit after college radio embraced the title track, "Buena," and "Thursday." Their songs appeared in the film Spanking the Monkey and, more recently, in the television series Beef and Euphoria — a sign of the band's continued reach among listeners who never saw them play live.

The Cocoon track list runs: "Tomorrow," "Wig," "Patience," "Spaceman Charm," "Justine," "Moons of Jupiter," "Cocoon," and "Pretty Face."

With new saxophone parts recorded by Colley and remixes supervised by the producer and archivist closest to Sandman, Cocoon stands to be the most definitive presentation yet of a body of work that has until now lived only in fragments on bootlegs and compilations.