Aaahhing

I can't call it cooing, because it has no "ooh" sound, so I'll call it "aaahhing".  When we're in a playful mood, if Finn looks directly at my face and I open my mouth wide and make the sound "Aahh" with either an ascending or descending scale, more often than not, he will open his mouth wide too and many time little "aahh" sounds come out.  So far he only does it when he is mimicking me.