Regional music festivals have become so commonplace that nearly every major city or scene has one. With San Francisco's Noise Pop, New York's CMJ Music Marathon, Boston's NEMO conference, Austin's South by Southwest, Portland's North by Northwest and Toronto's North by Northeast, it seems inevitable that everyone's hometown will play host to some sort of sonic symposium sooner or later. No other festival, however, covers American music with such depth and diversity as the New Orleans Jazz & Heritage Festival.

Seven-time Grammy nominee India.Arie and retro-rocker Lenny Kravitz are among the hundreds of artists slated to perform at the 33rd annual festival, according to organizers. Counting Crows, Bonnie Raitt, Melissa Etheridge and Blues Traveler round out some of the contemporaries planning to visit the Big Easy April 25 to May 5.

Most of the attending artists draw influence from traditional jazz, blues and roots music, evidence of which is most easily heard in the tunes of Wynton Marsalis, Dr. John and the Blind Boys of Alabama. Despite a successful effort by local merchants to ban Phish from future 'fests because their 1996 appearance brought throngs of fans who clogged streets and impeded pedestrian traffic, jam bands, whose improvisational tunes are in line with jazz's tangential trappings, have since made a strong showing. This year's crop of improv instrumentalists includes Ratdog, Gov't Mule, Karl Denson's Tiny Universe and the String Cheese Incident.

And, as always, local yet nationally renowned artists such as Better Than Ezra, Buckwheat Zydeco, and the Neville Brothers will also appear at the 11-day jamboree.

Tickets for the 33rd annual New Orleans Jazz & Heritage Festival went on sale Monday.