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.

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.

Five additional shows have been added to current trek.

Three Led Zeppelin covers were among the highlights of the show.

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

There have been vanity projects, weird detours and huge disappointments – but also some of the best LPs of the succeeding eras.

"I still don’t know enough to stop in any respect," singer said of his continuing career.

He wondered if they could repeat the artistic success of ‘Raising Sand’ some 14 years later.