The song is predominantly upbeat , featuring Bieber 's R&B vocals over a backdrop containing a dance infused beat , full of keyboard and `` disco string '' synths . The song is composed in the key of E ♭ major with Bieber 's vocal range spanning from the low - note of G to the high - note of C. According to Jody Rosen of Rolling Stone , the song `` blends winks at Fifties doo - wop with hip - hop chants '' , comparing the style and the lyrics `` My first love broke my heart for the first time / And I was like / Baby , baby , baby , ooooh / I thought you 'd always be mine '' to fifties ballads like `` Tears on My Pillow '' , `` Why Do Fools Fall in Love '' and `` Earth Angel '' . Lyrically , Bieber 's lines explain his distress over his lost love , and promise to get it back , featured in lines like , `` And I wan na play it cool / But I 'm losin ' you ... / I 'm in pieces / So come and fix me ... '' . The chorus features the distinct and repetitive `` baby , baby , baby , ohhhh ( nooooo ) '' hook . After the second verse , Ludacris comes in with the verse - rap , an anecdote of young love when he was thirteen , as it runs `` When I was 13 / I had my first love / She had me going crazy / Oh , I was star - struck / She woke me up daily / Do n't need no Starbucks ... '' .

Question: who sings the rap in baby by justin bieber
Answer: Ludacris