Is parody a viable defense to claimed copyright infringement of a purely musical composition by the author of the initial work?
Copyright infringement can be proved circumstantially by showing similarity and access. A musical composition (without lyrics) created solely to be melodically similar to the initial copyrighted work will almost always infringe that work by definition (unless it is solely a parody of the music alone). An example of a permissible parody of a musical work (without lyrics) may exist, but I am unaware of it. Notwithstanding, generally, you can’t copyright a harmony or a rhythm (because, in that event, nobody would be able to play music).
It is usually a factual issue as to when the fixation of harmony, rhythm, and timbre rises to the level of a melody, or, passes the threshold requirement for copyright under the DMCA at 17 U.S.C. 101 et seq. (“an original work of authorship fixed in a tangible medium of expression”). Likewise, whether a work is a parody, or not, is usually a factual issue for the jury.
It was my understanding that “Weird” Al Yankovick had to get permission from Madonna and others to do his musical parodies containing the “note for note” scoring of the original hits.