With the majority of existing Grateful Dead shows already released or well-leaked from the band’s tape vault, most new CDs in the ongoing Dave’s Picks series aren’t revelatory new discoveries, so much as excuses for Deadheads to time-travel en masse to a certain spot in the band’s space-time continuum. Popping out in New England in the spring of 1973, one finds three-and-a-half hours of maximum Grateful Dead chooglioogliness and a paucity of slow tunes in an era known for them. The band highlights its newest material, mostly Jerry Garcia’s, including a standalone second set “Stella Blue” (the first time Jerry Garcia sang the lyric about making his rusty strings shine, before that he couldn’t keep from cryin’) and a majestically belted “Mississippi Half-Step” (with casually shimmering vocal coda). But it is Bob Weir’s beautifully rendered “Weather Report Suite Prelude” that sets up an hour-long fantasy sequence of “Dark Star” into “Eyes of the World” into “Playing in the Band.” Neither segue is particularly smooth, but the jam-thread between the three songs is strong, including bright Weir-led high-wire dances in a 30-minute “Dark Star” that dissolve to spare night terrors, buzzsaw guitar, thromping bass chords and a slowly dawning “Eyes of the World” that casts golden Garcia solos on the New England heads. “Playing in the Band” is high-speed Dead-jazz, never dissolving fully, sailing back into the high-speed invention that the Dead could conjure at will in the early ‘70s and a marvel of any spot on the space-time continuum.