Logic frozen when loading projects with multiple JUCE'd AUv3 instances


I found an issue that AUv3 plugin made with JUCE causes Logic Pro X frozen when save and load a project contains multiple plugin instances.

An AUv3 plugin made with JUCE is installed. A simple plugin that is just built based on the template can reproduce the issue.
Mac OS X Catalina 10.15.7, Logic Pro X 10.6.1

Repro Steps:

  1. Launch Logic Pro X and create multiple software instrument tracks, load AUv3 synth instance for each. In my case, I created 7 tracks.
  2. Create MIDI region that contains some notes for each track.
  3. Save a project and close the project.
  4. Load the saved project.


  • Load project successfully.


  • Logic Pro X freezes, cursor goes to infinite rainbow. Plugin seems not loaded completely (the plugin name is grayed out). 100% repro.

This does not happen for non-v3 AU. Checked JUCE 6.0.0, 6.0.5, and latest develop build and all repro.

Not sure if this is caused by JUCE or Logic. Does anyone sees the same issue?

Thanks for raising this. The issue should be resolved by this commit:

1 Like

Thank you for fixing this quickly! I’ve verified the fix with my plugin.