By 1973 the Grateful Dead had entered the second era of its 30-year run (1965-95). With the death of singer Ron "Pigpen" McKernan that March, the band had lost its bawdy blues soul. But Bob Weir's full flowering as a rhythm guitarist and songwriter gave the band another front man in addition to Jerry Garcia.

The band's songwriting prowess and productivity also transformed the structure of its shows -- from free-form jam-fests taking off from a handful of numbers the musicians played most every night to performances centered on their growing stable of songs. The Dead could still unleash 40-minute jams, but the improvisational playing was increasingly corralled between the lyrics of set numbers.

The superb new nine-disc box set, "Winterland 1973: The Complete Recordings," captures the band on three hot November nights at its favorite San Francisco venue. The band rips through 72 songs in its inimitable blend of country, folk, jazz and psychedelia.

The recordings include spirited performances of new songs that would become Dead classics -- including "Row Jimmy," "Stella Blue," "Eyes of the World" and "Weather Report Suite/Let It Grow" -- and favorite covers such as "Big River," "El Paso" and "Promised Land." The band's harmonies are more ragged than right, but the playing is inspired throughout.

The set's centerpiece is two monster jams that look forward and backward. An epic 35-minute "Dark Star" recalls early interstellar journeys; a 43-minute jam featuring "Playing in the Band," "Uncle John's Band" and "Morning Dew" is a harbinger of later-era shows that would be built around the flow of songs into and out of each other.

"Winterland 1973" ($99.99) is only available online at www.dead.net.