Audio Units can come in all shapes and sizes, and there are certainly some weird and wonderful examples. Speak Unit is just such an example. Speak Unit is a speech synthesiser audio extension for use in Garageband or any other AU host you use. You enter up to twelve phrases that are each triggered by a unique note.
The developer says that it’s:
Ideal if you need robotic vocal for your musical compositions, or any other creative uses.
You can also use the app in stand alone mode to speak the phrases triggered by a row of note buttons.
The app reminds me of an app that Retronyms made a long time ago called Vox 3000. Sadly that app has long since gone, but it was very similar, and a lot of fun too. Hopefully Speak Unit will be just as good.
Speak Unit costs $0.99 on the app store now: