This specific minor update (3.6.6) focused on bug fixes and performance refinements to ensure the software doesn't crash during a live gig. Why "AllMacWorld"?
Attributes in the Screen Control Inspector now automatically update to reflect newly selected mappings, even if the MainStage application was hidden and then brought back to the foreground. MainStage-3.6.6.dmg - allmacworld
Version 3.6.6 includes a "Safe Mode" button on channel strips. If you have a complex concert file with 50 patches, enable Safe Mode on strips that do not change between patches. This prevents the CPU from reloading reverb tails and causing audio glitches. This specific minor update (3
: macOS Big Sur (11.0) or Monterey (12.0) was typically required for this specific version, though later updates shifted requirements to macOS 13.5 and above. MainStage-3.6.6.dmg - allmacworld