Michael McDonald first made it into the public's ear when he sang back up on Steely Dan's Katy Lied. He then hit his stride with the Doobie Brothers, and went on to appear on a lot of other artists's albums. He didn't have to be on them long - those distinctive pipes only needed a few moments to work their magic.
SCTV parodied this with their imagining of how the studio sessions went for the Christopher Cross song "Ride Like the Wind." Somehow, I can't help thinking this isn't far from the truth.