# AU Plugins

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 Audio Effect placeholder will appear.

AU (Audio Unit) plugins are .component files located in the user or system Library/Audio/Plug-ins/Components folder. macOS comes with several AU plugins, and many third parties offer AU plugins as well. Virtually all AU plugins are AUv2. Some newer ones are AUv3. MultitrackStudio supports both versions.

AU plugins can be loaded into an effect slot using the slot's down arrow. The AU plugins appear in the list's Plugins section. The plugin will be shown in a window with Bypass and Presets buttons. Any presets that come with the plugin appear in the Presets menu.

If an AU plugin gets into a bad state, you can press Command-R while the plugin interface is visible. This will save the settings, reload the plugin, and load the settings again.

Some plugins generate MIDI data. This MIDI output is merged with the data coming from MIDI input devices if the plugin is in a recording audio track and Soft Monitoring is enabled. MIDI output from plugins is only converted from MPE to MIDI 2.0 if the plugin either sends MPE configuration messages (RPN 6) or reports that it supports MPE (as per the MPE specs).

Note: If you install AU plugins while MultitrackStudio is running, you may need to restart MultitrackStudio for the new plugins to appear (the plugin list is collected only once).