# AU MIDI Effect Plugins

Note: AU Plugins are supported in the Mac version only. If a song with an AU plugin is opened in MultitrackStudio for Windows, a Missing MIDI Effect placeholder will appear.

An AU MIDI Effect is an 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 Plugins section.

Note: The "Apply in editor" option relies on plugins being able to save and restore settings, so it won't work with demo versions that can't do this.

### MIDI 2.0 / MPE

Starting with macOS 12, AU plugins that support the MIDI 2.0 protocol will receive MIDI 2.0. AU MIDI effects do not receive per-note controls otherwise.
MIDI output from plugins is converted from MPE to MIDI 2.0. You can avoid this by setting the per-note pitch bend range to zero. In this case, MPE to MIDI 2.0 conversion will only occur if the plugin sends MPE configuration messages (RPN 6).