 At the length of three minutes and thirty @-@ five seconds ( 3 : 35 ) , " Birthday " is primarily styled in the genre of disco . " Birthday " is composed in the key of B major and follows a progression of <unk> – C ♯ m7 – <unk> – C ♯ m7 – B with a tempo of 126 beats per minute . Perry 's vocals range from B3 to F ♯ 5 . During a preview event for Prism , held in New York City , Perry described " Birthday " as her " attempt at writing " a song that American singer and songwriter Mariah Carey would have included in her eponymous debut album . Since its release , its musical composition has been strongly compared to that of other works of Prince and duo Wendy and Lisa . 
