The first Grateful Dead album since Jerry Garcia’s death, “Grayfolded,” is not a typical Grateful Dead record. It’s one song that lasts 136 minutes, stretching through two compact disks, and was recorded over 25 years.

If this sounds strange and confusing, it’s because the person behind “Grayfolded” (Swell/ Artifact) is John Oswald, a Canadian composer best known for his digital manipulations and alterations of pop songs (which he calls plunderphonics).

Three years ago, Oswald was invited by the Grateful Dead bassist, Phil Lesh, to step into the band’s music vaults and see if he could create a project.

Oswald chose one of the Dead’s best-known songs, “Dark Star,” and walked away with recordings of more than a hundred performances of the piece, which he twisted, tweaked and layered into one long jam.

There is a lot to keep Deadheads busy on “Grayfolded”: choruses of Jerry Garcias young and old sing together, Grateful Dead keyboardists who have died have a duet and 64 snippets of Bill Kreutzmann’s drumming are stuffed into a oneminute solo.

As to the timing of the release, so close to Garcia’s death Aug. 9, Oswald said it was “awkward.” He added, “There’s going to be a perception that this is one of those quickie things thrown together after someone dies. But it’s not that sort of project. It was several years in the making.”