The pairing performed a medley of a pair of classics, "Long Train Runnin'" and "Takin' It To The Streets", on the program and recorded a web exclusive take on their 1979 No. 1 US hit, "What A Fool Believes."

A former member of Steely Dan, McDonald joined The Doobie Brothers in 1975 and his distinctive vocals were a defining part of the group's biggest hits of the era.

McDonald has occasionally performed with his former band in concert and appeared on 2014's "Southbound" album, which saw the group joined by a series of special guests to duet on re-recorded versions of some of their classic tracks.