Photo of Selena Gomez & Justin Bieber, courtesy Rex Features

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After years of an on-again, off-again relationship, Justin Bieber and Selena Gomez have joined forces for an unexpected musical collaboration "Strong."

The song, which debuted Saturday evening on Drake's OVO Sound radio show on Beats 1, finds the singers—who are now friends but not connected romantically—singing about a relationship gone south.

Hear a radio rip of the track below.