Thank you for all the great feedback! It sounds like there is a bug in version 4 of the plugin to do with "midi only" generating (from the Custom... menu or the preferences setting) that did not exist in version 3. To be clear, the function of the "Midi Only" option in the Custom... menu is to not generate the audio files for MIDI-Only styles. If you tried generating a MIDI-Only style and saw that AUDIO RealCharts (.wav) files were generated, than this is a bug. I'll look into this issue and try to fix it for the next build.