|Note: AU Plugins are supported in the Mac version only. If a song with an AU plugin is opened with MultitrackStudio for Windows a Missing MIDI Effect placeholder will appear.|
An AU MIDI Effect is a AU Plugin that can process MIDI messages. You can select an AU MIDI Effect by clicking the MIDI effect slot's down arrow. The AU MIDI Effect plugins appear in the list's 'VST and AU Plugins' section.
Note: the 'Apply to track' option relies on plugins being able to save and restore settings, so it won't work with demo versions that can't do this.