For a while the default path to the midi player was set incorrectly. This is now fixed, but the wrong setting is stored in the config file, so if you miss music, either you have to delete openttd.cfg to reset all settings and use at least 0.4.0 or you can edit it using a text editor like TextEdit. If you edit, find the line
Code:
extmidi = OpenTTD.app/Contents/macosx/track_starter
remove the x, so it says
Code:
extmidi = OpenTTD.app/Contents/macos/track_starter
Edit: unstickied this one as it applies to pre Quicktime midi only, which means it applies to 0.4.0.1, but not svn