PROVIDENCE, R.I. (AP) — On the night of July 25, 1965, Bob Dylan strode onto a stage at the Newport Folk Festival, plugged in an electric guitar and gave the music world a shock. Wearing a black leather jacket, the darling of the folk movement and singer of protest songs launched into a searing, distortion-filled, three-song electric set that brought boos from folk purists but thrilled others. Fifty years later, it's considered one of the most important events in rock history, the high-voltage moment when Dylan broke away from folk and helped show fellow musicians the poetic possibilities of rock. [...] the three-day festival, which starts Friday, is marking the anniversary with a closing-night tribute to be performed by a still-secret lineup of artists. Peter Yarrow of the folk trio Peter, Paul and Mary, who introduced Dylan that night, agrees Dylan was a poet pursuing his artistic vision. [...] he says Dylan's going electric had a different meaning back then for those in the folk world, which was deeply concerned with social causes such as civil rights. [...] they thought Dylan, who wrote "Blowin' in the Wind," and "A Hard Rain's A-Gonna Fall," was, too. [...] many in the audience had already heard one of the electric songs he played that night, "Like a Rolling Stone," which had been released the previous week and was on the radio. Legend has it that festival organizer and folk music elder statesman Pete Seeger threatened to take an ax to the power cord, though Wald says those stories probably stem from Yarrow telling the crowd Dylan was going to get his "ax," slang for guitar.