Did John Lennon and Elton John ever have songs on the music charts at the same time?
Yes. Late 1974: John Lennon singing “Whatever Gets You Through the Night” (background vocals and keyboards by Elton John). “Lucy in the Sky with Diamonds” by Elton John (background vocals and guitar by John Lennon). An unusual set of circumstances to be sure. For the record, both singles reached #1 in the USA.