in the opening chorus, and a Dm–C/E–C7–B–F/A sequence in the verses. The album version features bass guitar by Guy Pratt doubled by an analogue Minimoog bass synthesizer, while the 7" version has a different bass part played by Randy Jackson. "Like a Prayer" was also remixed by Shep Pettibone for the 12" single of the song; a re-edited version of Pettibone's mix is featured on Madonna's 1990 compilation album The Immaculate Collection. The song begins with the sound of heavy rock guitar that is suddenly cut off after a few seconds, and replaced with the choir and the sound of an organ. Madonna sings the opening lines accompanied by light percussion, as drums start during the first verse. The percussion and the choir sound are added interchangeably between the verses and the bridges, until the second chorus. At this point the guitars start flickering from left to right, accompanied by a bassline. Rikky Rooksby, author of The Complete Guide to the Music of Madonna, commented that "Like a Prayer" was the most complex track that Madonna had ever attempted at that point. He believed that the complexity builds up more after the second chorus, when the choir fully supports Madonna's vocals and she re-utters the opening lines, but this time accompanied by a synthesizer and drum beats. While singing "Just like a prayer, your voice can take me there, Just like a muse to me, You are a mystery", an R&B-influenced voice backs Madonna. The song ends with a final repetition of the chorus and the choir gradually fading out. Author J. Randy Taraborrelli noted in his book Madonna: An Intimate Biography that the lyrics of the song consist of "a series of button-pushing anomalies". With Madonna's inclusion of double entendres in the lyrics, "Like a Prayer" sounded religious to him but has an undertone of sexual tension. This was demonstrated by the use of a gospel choir, whose voice heightens the song's spiritual nature, while the rock guitar sound keeps it dark and mysterious. For O'Brien, the lyrics describe Madonna receiving a vocation from God. Certain portions of the lyrics also alluded to Sean Penn and their failed marriage. According to Priya Elan from NME, the line "Just like a muse to me, You are a mystery" was an example of this, befitting the description of an unattainable lover. This was also evident in the artwork for the 12"