PSA: Don't update to iOS 12.4 if you use apps in AB output slot or IAA apps that use the mic.
https://forum.audiob.us/discussion/34030/urgent-psa-hold-off-updating-to-ios-12-4-if-you-use-apps-in-output-slot-in-audiobus

Audiobus Forum

Discussion forum for Audiobus, the app-to-app audio platform for iOS and anything related to mobile music.

Discussion List