This article presents two new hypotheses about Brahms's Alto Rhapsody, op. 53 (1869), a work Brahms referred to as his "bridal song." Consulting a range of nineteenth-century sources, I explore the implications of rhapsody as a genre for this composition and argue that they include the classical convention of rhapsody as a poetic cento, or Stoppelgedicht. Centos, poems made up of quotations from earlier works, were often written for important events such as weddings; examples include the Cento nuptialis, which was discussed, among others, by August Wilhelm Ambros in his Geschichte der Musik (1864). Brahms's musical sources include Wagner's Tristan und Isolde and several works based on Goethe's Faust, including, especially, Liszt's Faust-Symphonie. My second hypothesis is that Brahms likely composed his Schicksalslied, op. 54, as a companion piece to the Alto Rhapsody. The two pieces respond to each other through several shared musical and textual correspondences. They deal in paired ways with the division between mortal suffering and otherworldly grace, and they embrace conventions and characters from antiquity. Invoking a concept proposed by Lawrence Kramer, I interpret these works as "expressive doubles" of each other. My investigation suggests that Brahms probably began work on the Rhapsody at least a year earlier than previously thought. © 2012 by the Regents of the University of California. All rights reserved.