Alison Krauss

It was announced on Friday afternoon that Nelson would be taking a few days off per doctor's orders.

Live version of the Led Zeppelin classic is the duo's first official release in two and a half years.

Duo began their trek with a performance in Tulsa, Oklahoma.

Country legend Willie Nelson's Outlaw Music Festival will return to Pine Knob in Clarkston on September 15, along with Bob Dylan and John Mellencamp.

The trek begins June 2.

Gov't Mule, the Avett Brothers and many other acts will appear on various dates.

The duo's March performance at Red Rocks will be available as a worldwide stream.

Led Zeppelin legend felt "exposed and vulnerable" as duet album ‘Raising Sand’ began to form.

Lead single "Can't Let Go' finds the duo covering Lucinda Williams.

One of the songs Plant recorded alongside Alison Krauss was "a hell of a challenge."