I have a recording of a duet with Al Jolson and Bing Crosby Alexander’s Ragtime Band (1947), which Jolson had a hit with previously in 1911. Crosby went on to do a duet on a Christmas special with David Bowie of The Little Drummer Boy (1977). David Bowie has done a duet with Moby, Cactus (2002).
Are there any other chains of duets like that which are as long or longer?
Picking up the original chain from the Bing-Bowie connection:
Bowie dueted with Queen on “Under Pressure” (1980)
Queen dueted with George Michael on “Somebody to Love” (1993; Freddie Mercury Tribute Concert version)
George Michael dueted with Mary J. Blige on “As” (1999)
Mary J. Blige dueted with Ja Rule on “Rainy Dayz” (2002)
Ja Rule dueted with Lil’ Wayne on “Uh-Ohhh!” (2009)
Lil’ Wayne dueted with Nicki Minaj on “Knockout” (2010)
Nicki Minaj dueted with Rhianna on “Fly” (2011)
Rhianna dueted with Jay-Z on “Talk That Talk” (2012)
Jay-Z dueted with Justin Timberlake on “Holy Grail” (2013)
Justin Timberlake dueted with the late Michael Jackson on “Love Never Felt So Good” (2014)