Prepare to be amazed. :)
Our little chatterbox has been making the "mmmm" sound for awhile now and yesterday started doing this. I promise he isn't actually sad - I think to get that sound out he has to make the pouty face.
Even though he has no clue what he's saying, I love that he's learning to mimic us. Next up - dadadadada. :)
(The best is starting around 40 seconds ...)