It’s the singer, not the song or is it? After all, it is the melody that lingers, the words that capture the undefinable. Songs are mercurial things, each having a mystery path — so far from the iPod or radio dial — that evades the fan. But next weekend, at various locations across the Island, the Martha’s Vineyard Songwriters Festival brings a dozen of the nation’s best songwriters together to celebrate songs, stories and each other.

“Newfoundland is a beautiful, dangerous place,” laughs Great Big Sea’s Sean McMann, about the locale that forged his band’s sound. Part shanty reel, part chiming pop, part sweeping folk, ten albums in, the little band from the island that was a shipping and fishing outpost between Mother England and Canada has let its isolation protect their individuality.

The laugh is still that down low rumble of thunder and a box car about to go out of service, and blues-folk legend Taj Mahal laughs a lot. It’s not just a survival strategy for the guitarist who burst into public consciousness in the sixties, but more the reflection of a love affair with life that has informed the roots icon’s journey through the shifting tides of American music over the last four decades.

Grace Potter is two hours into her summer tour and she’s already laughing. The woman who throws herself at a Hammond B-3 organ with a force that can only be described as feral retains her cheerful sense of rock and roll social awareness.

“Yeah, we’ve got a new vehicle,” she reports. “A sprint-er.”