Wikipedia
Stack-O-Tracks is an album release by The Beach Boys containing backing tracks to fifteen of their songs spanning their career to that point. This type of release was unique for the band, and generally is unique throughout the music industry where backing tracks, in the rare event of their commercial release, are generally bonus tracks or b-sides to singles.
The Beach Boys third and final album release of 1968, coming after Friends and released the same day as the quickly gathered material for Best of The Beach Boys Vol. 3, Stack-O-Tracks was seen by many at the time as a desperate last-ditch effort by Capitol Records to try anything to sell Beach Boys material. The strategy backfired, however; issued at one of their lowest commercial ebbs in the U.S., Stack-O-Tracks became the first Beach Boys album to fail to reach the U.S. or UK charts. Until 1992's much-maligned Summer in Paradise, it would remain their only official release to have this distinction.
The album included a booklet with the bass lines, lead lines, chords and lyrics (to sing along with). Stack-O-Tracks quickly disappeared and was out of print for two decades. In 1990, Capitol Records re-issued it on CD, and again in 2001 - both releases without the booklet that accompanied the vinyl edition.