[MusicXML] Title, Subtitle, Composer and Lyricist not exported
1. Open attached score.
3. Choose 'MusicXML'.
4. Open MusicXML.
Result: Title, subtitle, composer and lyricist aren't there.
Discussion: Marked critical as it represents a loss of information.
Using MuseScore 2.0 Nightly Build (5133) - Mac 10.6.8.