Studies of allusion, modeling, paraphrase, quotation, and other forms of musical borrowing hinge on the claim that the composer of one piece of music has used material or ideas from another. What evidence can be presented to support or refute this claim? How can we know that the material is borrowed from this particular piece and not from another source? How can we be sure that a similarity results from borrowing and is not a coincidence or the result of drawing on a shared fund of musical ideas?
These questions can be addressed using a typology of evidence organized into three principal categories: analytical evidence gleaned from examining the pieces themselves, including extent of similarity, exactness of match, number of shared elements, and distinctiveness; biographical and historical evidence, including the composer’s knowledge of the alleged source, acknowledgment of the borrowing, sketches, compositional process, and typical practice; and evidence regarding the purpose of the borrowing, including structural or thematic functions, use as a model, extramusical associations, and humor. Ideally, an argument for borrowing should address all three categories.
Exploring instances of borrowing or alleged borrowing by composers from Johannes Martini and Gombert through Mozart, Brahms, Debussy, Ives, Stravinsky, and Berg illustrates these types of evidence. The typology makes it possible to evaluate claims and test evidence for borrowing by considering alternative explanations, including the relative probability of coincidence. A particularly illuminating case is the famous resemblance between the opening themes of Mozart’s Bastien und Bastienne and Beethoven’s Eroica Symphony, discussed by hundreds of writers for more than 150 years. Bringing together all the types of evidence writers have offered for and against borrowing shows why the debate has proven so enduring and how it can be resolved.