"Here's an interesting one that I came across about a decade ago - Gulzar's non-film song 'kaash ek baar kabhi' is a Hemant/Asha tandem, but with a caveat. Asha recorded her version about 10 years after Hemant and her version starts with the antara 'raat chup chaap dabe paanv' instead of the mukhda 'kaash ek baar'; so I'm not sure if this falls within the definition of tandem - it's more of a version song. "
Requesting members to throw some light on this please