The Fruit performed backing vocals. The song was then mastered by Joe Gastwirt. Composition "Beat of My Heart" is an up-tempo new wave-inspired electropop song that incorporates elements of bubblegum pop and dance music in its production. It contains a "soft electronic pop" sound and has the heart beat sound as its base, as well as guitar strums at a "feverish pace" throughout the song. Spence D. of IGN described "Beat of My Heart" as a "glorious uninhibited slab of Euro pop as filtered through the vocal chords of a warm-blooded American girl." "Beat of My Heart" opens with the sound of a beating heart. In the pre-chorus, Duff's vocals are made distant by the song's use of guitars and synth keyboards. She sings that she is going to follow her own interests: "To the beat of my / To the beat of my / To the beat of my heart". In the first verse, a disinterested Duff sings that she is eager to speak her mind and "yield to her every desire". In the chorus, she sings that her confidence has strained her relationships with her friends. In the second verse, she sings of being over her depression. An "angry guitar" and a "goth piano" interrupts the song in its bridge. Duff sings that she is only listening to herself from now on. According to Chuck Taylor of Billboard magazine, the line "beat of my heart" is repeated forty-four times in the song. Critical response "Beat of My Heart" received generally mixed reviews from contemporary music critics. Pam Avoledo of Blogcritics wrote that Duff sounds like she is bored and "going through the motions" on the song. She further stated that Duff has "lost her sauciness and ironically, her spunk" in the song. Avoledo concluded her review by calling "the bland electro pop" song an "insult to the genre. It's like spilling ramen on a Vivenne Westwood evening gown." A reviewer from CBBC Newsround commented that the song is so repetitive that you will feel like "you've listened to it 20 times after just one play". The reviewer praised the heartbeat present on the track, writing that it "make it a bit of a foot-tapper", but deemed the lyrics to be "meaningless". The reviewer concluded that: "You'll find yourself humming it but will be hard pushed to remember what on earth she was singing about!" Spence D. of IGN