As I’ve mentioned, as a fan of Steely Dan, I was happy to see the Doobie Brothers were selected for the Rock and Roll Hall of Fame in 2020. That means contributing Dan vocalist Michael McDonald got in. When Dan pared down to a duo plus session musicians, I thought McDonald’s singing was integral to the sound.
That said, I was a big fan of the Doobies before McDonald joined the band. Of course, his addition was out of necessity, as founding member Tom Johnston was very ill. And his presence changed the alchemy of the band.
The Warner Brothers Loss Leader Leader called Cookbook (1977) was “Focusing on Warner’s black acts.” The only predominantly white group represented on the 2-LP set was the Doobie Brothers doing Taking It To The Streets, which went to #13 pop and #57 RB in 1976.
On the next few albums, McDonald dominated the sound, leading to some band acrimony, which Wikipedia covers well. One of the truly remarkable things about McDonald is the sheer number of albums he has appeared on, as a vocalist, keyboard player, and/or songwriter for other artists.
Occasionally, it was felt, he/the Doobies was competing with other songs he contributed to, which in time diminished the McDonald commercial appeal. But he and the group have gotten together occasionally.
Some songs
As a solo artist, he put out several albums, including Motown and Motown Two, well-regarded cover albums of… I’m guessing you can figure that out.
Doctor Wu – Steely Dan, 1975
Red Streamliner – Little Feat, 1977
Peg – Steely Dan, #11 pop in 1978
What A Fool Believes – Doobie Brothers, #1 pop, #72 RB in 1979
Minute By Minute -Doobie Brothers, 14 pop, #79 RB in 1979
Ride Like The Wind – Christopher Cross, #2 pop for four weeks in 1980
This Is It – Kenny Loggins, #11 pop, #19 RB in 1980
Yah Mo B There – James Ingram ft MM, #19 pop, #5 RB in 1984 (Ingram, BTW, was born Feb 16, 1952, and died Jan 29, 2019)
On My Own – Patti LaBelle ft. MM, #1 for three weeks pop, #1 for four weeks RB in 1986
Sweet Freedom – Michael McDonald, #7 pop, #17 RB in 1986
Ever Changing Times – Aretha Franklin ft. MM, #19 RB in 1992
LIVE: Ain’t No Mountain High Enough/Ain’t Nothing Like The Real Thing – Michael McDonald with Ashford and Simpson. McDonald’s studio version of Mountain went #111 pop in 2004
I’m doing Favorite Songs by Favorite Bands thing that J. Eric Smith did. 
If you had asked me a couple weeks ago what I thought of Steely Dan, I would have said I liked them well enough, though I have rarely blogged about them in the 12+ years I’ve been doing this. But after Walter Becker, half of the core duo with Donald Fagan, 