What do you need to form a random doo-wop group with singing legend Billy Joel? Perhaps three other singers? Some talent? An arsenal of songs? Someone to convince Joel that he needs to be a in strange doo-wop group at this point in his career? Nope! Turns out, you just need a late night talk show and an iPad app.

On last night's 'The Tonight Show Starring Jimmy Fallon,' Fallon convinced Joel to trill away into, yes, an iPad app that loops voices so that the two of them could sing "The Lion Sleeps Tonight" in four-part harmony. (No, we won't mention that their little experiment was made immeasurably better, thanks to the live band behind them.)

And, as an added bonus, here are Jimmy and Billy doing a legitimate duet later in the show on Joel's classic "You May Be Right." Why is Jimmy singing during Billy Joel's musical performance? We're not sure, but he's sure having fun doing it.

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