For a band famously allergic to practicing, the Grateful Dead spent a lot of time in rehearsal in the run-up to Blues for Allah. 

Ninety minutes of those rehearsals, in which the Dead don’t sing and Bob Weir plays like a traditional rhythm guitarist, are now Blues for Allah: The Angel’s Share, a 50th-anniversary streaming-only album that follows similar treatments of Workingman’s Dead, American Beauty, Wake of the Flood and From the Mars Hotel. 

Recorded without Donna Jean Godchaux between February and July, the tapes reveal “Help on the Way” once galloped at triple speed and “Franklin’s Tower” began life as a loping track as Jerry Garcia mused aloud about finding the right groove. There’s also banter that finds the Dead talking and laughing among themselves as they work out and imagine future overdubs for “Sand Castles and Glass Camels” and rediscover the fun that, when it went missing, had led them their 1974 retirement. 

While instrumental treatments of album tracks and 1976 tour numbers like “Lazy Lightning/Supplication” and “They Love Each Other” are enlightening, it’s the true improvisations that really show listeners the light. “Distorto” is so named for Garcia’s guitar tone; “Proto 18 Proper” finds the band recasting the pre-retirement “Eyes of the World” jam as “King Solomon’s Marbles;” and “Jam/Blues for Allah” may contain the first example of “Lost Sailor”’s opening riff. 

“Surf Jam” isn’t really surf music but it is unique in the Dead’s canon. “Crazy Fingers,” meanwhile, owes little to the title and foreshadows the Jerry Garcia Band’s 1990s arrangement of “The Way You Do the Things You Do.” 

Coulda called that one “Reggae Jam.”