A hard, hard rain fell on the Grateful Dead concert at Merriweather Post Pavilion last night, and for a while it looked as if the lost tribes of Woodstock had gathered for a reunion.

On the lawn, before the downpour, thousands of self-styled Deadheads, many wearing tie-dyed T-shirts, frolicked barefoot in the mud, seemingly oblivious to everything but the loping rhythms played on-stage. It was rock as ritual, '60s style.

The concert, the season's first, began an hour and a half earlier than usual, presumably to accommodate the Dead's notoriously leisurely pace. On recent visits the group has divided its time between acoustic and electric sets, but this time electricity flowed for the duration, with the usual mixed results.

A Dead concert is one of the few constants in pop music: the guitar solos by Jerry Garcia and Bob Weir ranged from the insinuating to the indulgent; the vocals seemed either pale ("Little Red Rooster") or ingratiatingly folksy (virtually everything Garcia sang), and the choice of material offered no surprises, other than perhaps a particularly rousing version of Reverend Gary Davis' "Samson and Delilah."

But if the show was predictable, so was the response. Deadheads danced the dreary night away.