TORONTO -- A local audience got a chance to hear a brand-new Woody Guthrie song Saturday night during a concert by the Chicago-based band Wilco.

Last year, Wilco and Billy Bragg released the critically acclaimed "Mermaid Avenue" album, comprised of lyrics the legendary folk singer Guthrie wrote during his life but never completed as songs.

Wilco guitarist Jay Bennett recently told JAM! that the band had returned to the Guthrie archives in New York City to gather new lyrics for a second album of his songs, but Bennett said the group was not debuting any of the new material in concert and planned to begin recording shortly after their tour wraps up this month.

But during a technical problem part-way through the group's set at the Phoenix Concert Theatre on Saturday, singer Jeff Tweedy began performing an unidentified song with beautiful lyrics that sounded more like a medievel madrigal than either Wilco's twisted take on country or Guthrie's polemical folk music.

After one verse, Tweedy was soon joined by the full band. When they finished, Tweedy revealed the lyrics indeed were written by Guthrie.

"Don't those words f---in' rock?" the singer asked the crowd.

During the group's encore, Tweedy also paid tribute to recently deceased singer Doug Sahm, and performed his "Give Me Back The Key To My Heart," a song Tweedy's disbanded group Uncle Tupelo recorded with Sahm on their "Anodyne" album.

Sahm, 58, was leader of the seminal Tex-Mex garage rock band the Sir Douglas Quintet, but was found dead in a Taos, New Mexico hotel Thursday of an apparent heart attack. Tweedy also reminisced about Sahm tutoring Uncle Tupelo in vocal phrasing.

"That was good advice," Tweedy said.