The majority of Sunday Guitar users seem to do well with MainStage 3.4.2 on Mac OS Mojave, but some have reported issues with opening the Sunday Guitar template or copying/pasting.
Other ways to open Sunday Guitar:
- Open Mainstage 3.4 while holding down the option & command (⌘) keys. This always opens a clean session. Then, open a stock patch and then open your Sunday Guitar concert. This may also help your copying and pasting.
- Open a default MainStage 3.4 concert (keyboard or guitar), and then open Sunday Guitar from there.
- Open a time machine backup version of MainStage 3.3, and then open Sunday Guitar from there.