Michael Erlewine's devotion to studying and playing the music of Black Americans, in particular blues, led to his traveling to small blues clubs of Chicago and hearing live, blues greats like Little Walter, Magic Sam, Big Walter Horton, and many others. He went on to interview many dozens of performers. Much of this interviewing took place at the Ann Arbor Blues Festivals, in 1969 and 1970, the first electric blues festivals of any size ever held in North America, and than later at the Ann Arbor Blues & Jazz Festivals.

With their extensive knowledge of the blues music, Eriewine and his brother Daniel were asked to play host to the score or so of professional blues musicians and their bands. They were in charge of serving them food and (of course) drink. Michael went on to interview most of the performers in these early festivals, with an audio recorder, and later on with video.
The interviewing led to more study and ultimately resulted in Michael founding and developing AMG,the All-Music Guide, today the largest single database of music reviews and documentation on the planet.

Erlewine started from a one-room office, and the reviewers and music aficionados of the time laughed at his attempt to cover all music. But he persisted, and the all-Music Guide appeared as a Gopher Site, before the World Wide Web even existed-a database of popular music for all music lovers.

Over the years AMG grew, and the All-Movie Guide and All Game Guide were born, and also flourished. Later, Erlewine would create ClassicPosters.com, devoted to the history and documentation of rock n' roll posters, some 35,000 of them.

These guides changed the way music was reviewed and rated.Previous to AMG, review guides like the "Rolling Stones Record Guide" were run by a few sophisticated reviewers,and the emphasis was on the expertise of the reviewer, and their point of view . Erlewine insisted on treating all artists equally, and not comparing artist to artist, what can be important, Michael points out, is to find the best music any artist has produced, not if the artist is better or worse than Jimmie Hendrix or Bob Dylan.

Erlewine sold AMG in 1976, at which time he had 150 fulltime employees, and 500 free-lance writers. He had edited and published any number of books and CD-ROMs on music and film. During the time he owned and ran AMG, there were no advertisements on the site and nothing for sale. As Erlewine writes, "All of us deserve to have access to our own popular culture. That is what AMG and ClassicPosters.com are all about.” Today, AMG reviews can be found everywhere across the Internet. Erlewine's music collection is housed in an AMG warehouse, numbering over 250,000 CDs.