We have just released Inter-App Audio (IAA) support for standalone plug-ins on iOS as a JUCE 5 feature on the develop branch.
To make your standalone plug-in available as an IAA instrument or effect you need to compile the most recent version of the Projucer. The new Projucer provides a new plug-in configuration option, “Enable Inter-App Audio”, which does what you would expect. In many cases you will also want to enable “Microphone access” in the iOS Xcode build options.
There is a new, simple example plug-in located in
examples/PlugInSamples/InterAppAudioEffect which demonstrates some IAA-specific features such as controlling the IAA host’s transport, displaying the host’s icon, and switching to the host application. As a byproduct of the work we’ve done here it is now also possible to retrieve the icon of a conventional plug-in (VST, AU, …) host on OS X via the same mechanism.
Note that if you try building the JUCE Demo Plug-in as a standalone IAA app then it will be classified as a “Remote Music Effect” - an effect (i.e. not a synth) which accepts MIDI input - which is not supported by GarageBand. Enable the “Plugin is a Synth” option to both use the plug-in as an instrument and receive MIDI messages.
Please start using the new functionality and post any feedback or issues here.