Maroon 5's Adam Levine and No Doubt's Gwen Stefani are co-hosting together on NBC's The Voice, so, naturally, a collaboration was going to come into fruition from their friendship. M5's aptly-titled fifth studio album, V, is due out on Tuesday, September 2nd, and Gwen's contribution to their piano-driven "My Heart Is Open" has leaked online for fans to listen to. It's unsure whether or not Maroon 5 plans to release "My Heart Is Open," but it would definitely fare well on the charts. The gorgeous track has Levine crooning My heart is open / I'm letting you in / Cause you give me a reason and the faith I've been needing to start again. Stefani joins in with her verse, stating I can't wait anymore, no no / Because I've got nothing left to prove. Fun fact: the emotional ballad was co-written by Sia, which you can definitely hear when you listen to the song.