 Also, after the release of the first six volumes on CD, all of the tracks on the Pebbles CDs had been previously un-reissued on CD.Even the first two releases in the Essential Pebbles series include a second CD of previously un-reissued music in addition to the distillation from the previous Pebbles albums.According to the AIP website, ESD Records (also known as East Side Digital) issued 4 volumes of CDs in the "Pebbles series" in 1989–1990.