This was discussed on #scummvm earlier today. Currently, EGA Loom and EGA Monkey Island 1 will both error out if the user has selected a MIDI music driver but the Roland Upgrade file(s) are missing.
Fingolfin added a TODO that we should handle this case more gracefully, I suggested a possible patch, and Kirben corrected my bone-headed mistakes. This is Kirben's version of the patch, with some minor changes.
What it does is to move the test for missing files to setupMusic(). This is where we determine which music driver to use, which is a bit earlier than we currently do it.
Ticket imported from: #1709681. Ticket imported from: patches/756.
Patch against current SVN