The Grateful Dead played over 2,300 concerts and each one was completely unique due to their improvisational style. Jerry Garcia talked about how in every Grateful Dead concert, about 80 percent of the music was improvisation, and 20 percent was more like the standard, repeatable songs, similar to what other bands played at their concerts.
This improvisation wasn't new—jazz musicians had been doing it for years (and greatly influenced the Grateful Dead's style). In jazz performances, a member of the group begins a riff and runs with it, then another member picks it up and builds on it, and so forth. The improvisational elements are sequential with only one musician riffing at a time.
The Grateful Dead, however, improvised individually and as a group—at the same time. Musically, this simultaneous improvisation was profound as it required band members to listen carefully to what each of the other members were doing musically and build on it—while simultaneously carrying on their own improvisational riffs.
Truly passionate about experimentation, individual band members constantly worked with different instruments. Garcia, for example, played the electric guitar, bluegrass banjo, pedal steel ...