Although best known for his barnstorming blues-rock, Irish guitarist Rory Gallagher had a softer side, too.

All of his studio albums contain at least one acoustic folk-blues track, and Gallagher included an unplugged set in the majority of his live shows way before that was fashionable.

Almost eight years after his death, Rory's brother Donal compiled a 14-track collection of previously unreleased work dedicated to Gallagher's folkier approach.

It's the second such posthumous album (the terrific live and very electric BBC Sessions came out in 1999), and focuses on an important if lesser recognized aspect of the guitarist's career.

It's also an eclectic set that shifts from melodic ballads ("Wheels Within Wheels") to instrumental modified flamenco ("Flight to Paradise" with classical guitarist Juan Martin) and solo Delta blues (a studio take of Tony Joe White's "As the Crow Flies," the live version of which was a highlight of Irish Tour).

And that's just the first three songs.

Unreleased gems such as "Lonesome Highway" sound like classic Gallagher (this even features a plugged-in solo), but the disc is most successful when it unearths rare collaborations with Martin Carthy, Bert Jansch, and Scottish skiffle legend Lonnie Donegan.

The latter is caught live on a rousing version of "Goin' to My Hometown," one of this album's many highlights.

The heavily bootlegged "The Cuckoo," also finds official release in a stirring version assisted by Roland Van Campenhout on second guitar.

Three live tunes with stripped-down accompaniment from Béla Fleck on banjo and harmonica master Mark Feltham find Gallagher running through a seemingly improvised medley of "Amazing Grace," Robert Johnson's "Walking Blues," and Bill Monroe's "Blue Moon of Kentucky," showing just how diverse Gallagher's tastes were.

Established Gallagher fans will love this for the unusually laid-back setting, but Wheels Within Wheels might also attract a hardcore folk audience likely unaware of the rock guitarist's affinity for this genre.

The varying sound quality is a little sketchy, especially on the concert tracks, but the sheer enthusiasm and joy infused in these grooves override any audio shortcomings.