If GarageBand for Mac 6.0.5 on macOS High Sierra won't open
It can take up to 10 minutes for GarageBand for Mac 6.0.5 to open after upgrading your Mac to macOS High Sierra.
This only happens the first time you open GarageBand after upgrading to macOS High Sierra.
You can update to the latest version of GarageBand to avoid this issue. You can download the latest version for free from the App Store.