The file format of "capella" evolved from a proprietary digital encoding (filename extension *.cap) to an open, XML text based format called CapXML with extension *.capx. There are CapXML 1.0 and 2.0 formats. Each *.capx file is a ZIP archive containing the actual XML with filename "score.xml". CapXML differs from MusicXML in various aspects, one being that in CapXML the basic node is the chord which can have one or more notes, whereas in MusicXML the notes of a chord are single nodes which have to be put into relation with one another. Capella can import and export MusicXML files.