From Technology Review: Software Sorts Tunes:

This work taps a universal similarity metric the researchers previously used to construct evolutionary trees of animal species and Eurasian languages, and to detect plagiarism in student programming assignments.

The latest application shows that the method could be used to automatically categorize music, and to determine the true origin of music authorship.

The method measures how easily one file can be compressed using the information contained in a second file, then uses a parallel, hill-climbing algorithm to organize differences among files into a branching tree. Hill-climbing algorithms improve a solution at each step. To speed the process the researchers' algorithm examines many files in parallel.

I wonder how badly it would be confused by Hindemith's Symphonic Metamorphosis of a Theme by Weber, Vaughn Williams' Fantasia on a Theme by Thomas Tallis, Brahms' Haydn Variations (whose theme is now considered not to have been written by Haydn), Stravinksy's Pulchinella (based on music that he thought was by Pergolesi), etc.