Derek Jay Steen says:

Regarding ‘Ducking in Garageband’ — I leave it off when recording, and raise/lower audio in post production. It saves me from having odd peaks/silences, etc.

I’ve never really found the feature useful; raising the levels only when you talk sounds weird because of the ambient noise that comes with it. Unless, of course, you record in a sound-proofed room where ambient noise doesn’t exist.

E. Christopher Clark says:

Good points. I’m definitely going to try doing everything manually the next time (though this time it did actually turn out alright, after all).