Just what constitutes folk music has always been open to debate, but the term seemed unusually broad at Lisner Auditorium Saturday night when the World Folk Music Association held its third annual concert.

If the sold-out show had one common thread, it was that most of the performers were contemporary songwriters who favor acoustic music and who were inspired, at least in part, by the folk music revivals of the '50s and early '60s. Truth is, a lot of these musicians would have been equally at home playing for a pop, country, swing or, in the cases of headliner John Stewart and local favorite Pete Kennedy, even a rock audience. Indeed, Christine Lavin's uproarious set, complete with a baton-twirling number, could have played in a comedy club.

For sheer fun and laughter, Lavin was unbeatable. Like the other WFMA regulars on the bill -- Buskin & Batteau and Schooner Fare -- she's developed a strong following here over the past few years and continues to develop new and clever material.

Stewart was also impressive, singing a number of new and thoughtful songs in his distinctive incantatory style and mustering plenty of rhythmic momentum with the help of fellow singer and guitarist Chuck McDermott. Another highlight was Kennedy's brooding acoustic version of "19 in Vietnam," but there were lighter moments as well, including delightfully harmonious performances by Dramtreeo, Bill Danoff and Side by Side, Sassparilla with Laurel Blaydes and Irish vocalist Liam Maguire. Among Carolyn Hester's contributions were a heartfelt homage to the Rev. Martin Luther King Jr. and a topical ditty called "King Kong Blues." Anne Hills and Steve Gillette added nicely to the evening's collection of reflective ballads.

The show ended on a sentimental yet upbeat note, with three former members of the Kingston Trio -- Stewart, Dave Guard and Nick Reynolds -- robustly reprising "Tom Dooley" and other favorites before everyone joined them on stage.

Still, there was a dearth of traditional folk songs, and in a town that boasts numerous traditional blues artists, it seems a shame that none of them was represented. Indeed, there was only one black performer on stage all evening, and he was part of an ensemble.