the song. After finishing the lyrics, Madonna declared that she wanted the song to be named "Who's That Girl" and changed the movie to the same, rather than Slammer, considering it to be a better title. In Fred Bronson's The Billboard Book of Number 1 Hits book, Leonard explained that the song was recorded in one day with Madonna adding her vocals only once. Additional instrumental tracks with guitars and percussion were included by Leonard and Bray later. Regarding the development of the music for the film, Madonna further explained "I had some very specific ideas in mind, music that would stand on its own as well as support and enhance what was happening on screen and the only way to make that a reality was to have a hand in writing the tunes myself. [...] The songs aren't necessarily about Nikki [her character name in the movie] or written to be sung by someone like her, but there's a spirit to this music that captures both what the film and the characters are about, I think." The song is composed in Madonna's typical style—mingling the drum machine, a bass synth line, and the sound of stringed instruments. The three parts of the song, namely the bridge, where Madonna sings "what can help me now", the chorus and the verse flow together strongly. The chorus has a haunting effect in it. According to the sheet music published at Musicnotes.com, the song is composed in common time in the key of A minor, and performed at a medium tempo of 104 beats per minute. The song follows a basic chord progression sequence of Am9–G–Csus2–Am9–G–Dm and Madonna's vocals range from G3 to B4. The song epitomizes Madonna's interest with Hispanic culture that continued after the release of "La Isla Bonita", by adding Spanish phrases in the chorus and over the trumpets of the second verse, and also by the added instrumental break in the middle. It also uses the sonic effect brought about by the combination of multiple vocal lines, which had been previously used by groups like The Beach Boys in their singles "God Only Knows" (1966) and "I Get Around" (1964) as well as R.E.M.'s singles "Fall on Me" (1986) and "Near Wild Heaven" (1991). "Who's That Girl" employs this effect on the last chorus where three or four different vocal hooks are intertwined. Critical reception In his book The