Before version 3, QMidi stored synchronization data in the resource fork of linked text files. As macOS evolved, resource forks became deprecated and later converted into extended file attributes. In both cases, the data could be lost when transferring files—especially if they were sent without zipping or copied to a disk that did not use HFS+ or APFS.
Starting with version 3, all synchronization data is stored in a project package with the .qmid extension. This package is created automatically when you edit text, chords, markers, the MIDI mix, or the audio mix. The project file is saved in the same folder as the song and uses the same file name.
Contains your audio mix data, see the mixer help section.
Contains your MIDI mix data, see the mixer help section.
Contains your lyrics, chords, and marker data, see the text/chords/markers section.
If the text is formatted in RTF (Rich Text Format) and includes images, those images are stored inside the project package. (In versions prior to v3, this information was stored in RTFD files.)