The Grateful Dead fan base is so widespread and ravenous, it can support all sorts of spin-offs, tribute bands, deluxe reissues, official bootlegs, coattail-riders, etc. These aficionados are still the vital circulatory system of the lucrative jam-band corpus. Dead & Company have the benefit of featuring GD percussion deities Mickey Hart and Bill Kreutzmann and OG (not Jerry) guitarist Bob Weir, as well as white-bread guitar hero John Mayer, bassist Oteil Burbridge (Allman Brothers Band), and keyboardist Jeff Chimenti (Bob Weir & Ratdog). These pros reverently reanimate easygoing, glistening faves such as “Sugaree,” “Althena,” “Terrapin Station,” “Morning Dew,” “The Weight,” and others with expert precision and patience. That they possess the box-office clout to pack out two dates at the Gorge testifies to the durability of the Dead brand. by Dave Segal