The 'Rocket Man' singer spent two nights in intensive care after becoming "violently ill".
Chicago and Earth, Wind & Fire performed a medley on US show Jimmy Kimmel Live to promote their forthcoming tour.
The two groups, who are going on the road in the US this summer, combined forces and played a selection of their well-known hits on the late-night talk show. These included Earth, Wind & Fire's 'Sing a Song', Chicago's 'Does Anybody Really Know What Time It Is?' and Earth, Wind & Fire's 'Shining Star' with Chicago's Robert Lamm leading on some vocals.
Both bands formed in the late 60s have had massive success. Chicago has sold more than 100,000,000 records to date while the founding members of Earth, Wind & Fire have been inducted into the Rock and Roll Hall of Fame .
The Chicago and Earth, Wind & Fire – Heart And Soul Tour 2015 will kick off on 15 July in Concord, CA and see the 21 very talented musicians visit major cities across the 25+ tour dates. It will conclude on 6 September in Atlantic City, NJ.
View the YouTube video below to see the medley performed on Jimmy Kimmel Live :