Music information retrieval faces a tower-of-Babel problem. There is no musical format in widespread use today that overcomes MIDI’s limitations as an interchange format between performance, notation, analysis, and retrieval applications. A problem for past interchange efforts has been the absence of commonly used formats for complex structured data in general. XML provides the technical foundation for an interchange format that is more powerful and expressive than the current MIDI format. Developing converters between existing formats and a single music XML document type definition has the potential to greatly simplify the tasks of music information retrieval. MusicXML attempts to provide a common document type definition that is well designed from musical, human, and computer perspectives.