Over the years a number of studio rarities have been appended to the deluxe or expanded versions of The Grateful Dead’s studio albums. In addition, two critically acclaimed career-retrospective box sets—2001’s The Golden Road and 2004’s Beyond Description—further increased the number of “alternate” studio recordings available in their best fidelity. This collection (like its companion Complete Live Rarities Collection) mops up the loose ends in one spellbinding place. These tracks are best understood in context with the new digital book The Golden Road and Beyond: A Grateful Dead Primer, which has two essays written for those aforementioned box sets by the band’s longtime publicist Dennis McNally. However, you only need ears to enjoy the Scorpio Sessions versions of “Don’t Ease Me In” and “I Know You Rider,” the under-three-minute take of “Dark Star,” and the studio outtakes of “Catfish John,” “Jack-a-Roe,” and “Peggy-O.” The b-side “My Brother Esau” is a great find, while the studio rehearsal of “Touch of Grey” should interest anyone who fell under the spell of the band’s biggest hit single.