Identifying copies or different versions of a same musical work is a focal problem in maintaining large music databases. In this paper we introduce novel ideas and methods that are applicable to metered, symbolically encoded polyphonic music. We show how to represent and compare polyphonic music using a tree structure. Moreover, we put for trial various comparison methods and observe whether better comparison results can be obtained by combining distinct similarity measures. Our experiments show that the proposed representation is adequate for the task with good quality results and processing times, and when combined with other methods it becomes more robust against various types of music.