Rock history has had several pivotal periods when paradigms shifted significantly. 1964: The Beatles conquered America. 1969: Hippies became a defined nation of longhairs. 1976: Punk sneered its way into the culture. 1991: Alternative rock went from underground to mainstream.

That transition is indelibly spotlighted in Dave Markey’s concert documentary, 1991: The Year Punk Broke, reissued on DVD to celebrate the movie’s 20th anniversary. Markey followed Sonic Youth, Nirvana and to a lesser extent other likeminded groups on a European festival tour before Nirvana became famous.

A pre-celebrity Nirvana whips through raw renditions of “Negative Creep” and “Smells like Teen Spirit.” Sonic Youth rampages through fan faves like “Teenage Riot” and “Kool Thing.” And there’s much more.

Viewers take note: More than 60 minutes of supplementary material (much of it live) has been used to expand the original 90-minute presentation to 160 minutes, including Markey’s new DVD companion piece, the 42-minute short film, (This Is Known as) The Blues Scale, created from unused super-8 footage shot during 1991. Another addition is a 15-minute Sonic Youth Q&A from 2003 where band members discuss Markey’s film; some unedited live footage and an alternative edit for Sonic Youth’s “Teenage Riot.”

1991: The Year Punk Broke is currently available.