“I don’t know why thinking of him makes me smile,” Ariana Grande whispers at the beginning of her new duet with Mac Miller, kicking off three and a half minutes of warm, silky, soul-pop comfort.

“My Favorite Part” marks the third time Miller and Grande have collaborated, following his guest verses on last month’s “Into You” remix and her 2013 breakthrough single “The Way.” Things are much different this time around, though, given that the pair are now a legit couple — they’ve been spotted getting cozy together several times in the past few weeks, including at last month’s VMAs and even on Instagram.

On “My Favorite Part,” Grande’s angelic vocals and Miller’s raspy drawl melt together gorgeously, creating a hip-hop ballad that sounds “so divine” (Ari’s words, not mine). “You just don’t know how beautiful you are / And baby, that’s my favorite part,” Miller croons, taking a page from One Direction’s playbook, before assuring his lover he’s got her covered and the universe can’t keep them apart. Listening to it feels borderline voyeuristic — like you’re a fly on a wall during a private, intimate moment (or maybe just a third wheel). But when your chemistry is as sweet-sounding as this pair’s, why wouldn’t you share it with the world?

“My Favorite Part” appears on Miller’s upcoming album, The Divine Feminine. The LP hits shelves September 16 and also includes previously released tracks “Dang!” with Anderson .Paak and the breezy, Cee Lo Green–assisted “We.”