The Mac OS X version of Sibelius is capable of hosting both VST and AU plugin formats. However, there have been reports that later versions of Sibelius (version 8+) crashes on later versions of Mac OS X (El Capitan+) when using the VST version of Kontakt in a Playback Configuration. For that reason, it is recommended that the Kontakt AU plugin be used (rather than the VST) when using Kontakt within Sibelius 8+ on Mac OS X.
How to differentiate between AU and VST Kontakt Plugins
In Sibelius, VST and AU plugins can be selected from the available devices pane in Playback Devices window.
Within the Playback Devices window, a listing of available plugins (aka “devices”) will be listed on the left. If Kontakt is not listed, please consult this Knowledgebase article.
Most likely, you’ll see both AU and VST options for Kontakt. If you see three different VST versions, that’s okay. Just ignore those.
If Sibelius Crashes when Kontakt VST is selected
If selecting the VST plugin crashes Sibelius, try using the AU plugin. If Sibelius crashes when it is launched, a playback configuration using a VST plugin may have been set as the default configuration. That particular configuration will need to be deleted.
1. Quit Sibelius.
2. In Finder, hold down the ‘option’ key, and from the Go menu, select Library.
3. Navigate to Application Support/Avid/Sibelius X/Playback Configurations
4. Within the Playback Configurations folder, locate the offending configuration and delete its corresponding .xml file. If a data folder by the same name also exists, delete it as well.
5. Launch Sibelius again. The program should no longer crash. Just remember to use the AU plugin to avoid additional crashes.