- SynthScaper ver. 1.7.8 (does not use external input)
- SynthScaper LE ver. 1.2.3 (does not use external input)
- FieldScaper ver. 2.1.2 (USES external input!)
- SoundScaper ver. 1.9.6 (does not use external input)
But this update only partially gives workaround of this problem. Maybe in the future versions iOS this bug will be fixed.
All apps that work as an IAA instrument or effect but do not use recording from microphone will be work as usual without problems with IAA.
Under iOS 12.4, any IAA node app that records from the built-in microphone or audio input will fail to start IAA connection when launched into the background via IAA hosts like AUM, Audiobus, Cubasis, etc. The only way to recover the audio session is to manually switch the app to the foreground, but this will work only if the app has been fixed to workaround this problem.
There is a workaround in the latest version of Audiobus 3 that forces any node app that has an audio receiver port to always require a manual start. Some IAA hosts always bring an app to the foreground at startup (Cubasis). But in some others, you must manually click on the node's app icon to bring it to the foreground to start an audio connection.