"Stereo Hearts", produced by Benny Blanco and Robopop begins with Maroon 5's Adam Levine singing the hook: "My heart's a stereo / It beats for you, so listen close/ Hear my thoughts in every note. / Make me your radio / Turn me up when you feel low / This melody was meant for you / So sing along to my stereo." McCoy then raps about serenading his ideal girl and picking love over animosity, all the while relaying the message using music-based metaphors. Additional Fender Rhodes was played by Austin Bisnow at Chalice Recording Studios in Los Angeles, CA.
Gym Class Heroes drummer Matt McGinley explained that the song's music video "basically plays on the idea that we're sort of just being casual, hanging out, being ourselves and our shadows get wild and get loose. The video shows the band playing in the city of New York and their shadows are playing on the ground."
The video (directed by Hiro Murai) has the feel of a 1980s setting, with a breakdancer and several payphones seen, though the actual setting is modern as evidenced by the Mini Cooper in one scene. It prominently features a pawn shop with a stack of old-fashioned boomboxes and TV sets, on which Adam Levine appears when he is singing the chorus.
The lyric video for the song received millions of views in the first month of its release. This is one of the first lyric videos to incorporate a live action story line, showing a man and a woman in split-screen as they get dressed for the day and go outdoors carrying boom-boxes, until they finally meet in a park. The video stars actress Breana McDow and was directed by music video director Djay Brawner.
The song received positive reviews. MTV's Jenna Hally Rubenstein complimented the band's new direction on "Stereo Hearts", writing that it is "a little more slickly produced than we're used to, but, we're still solidly behind the experimental new song." MTV's James Montgomery described it as a "prime-time slab of genre-mashing, sweat-inducing pop, the kind of song that may very well push GCH to summertime superstardom." Becky Bain of Idolator called it a "head-nodding jam" and "an instantly memorable signal that Gym Class is back in session."