I had that happen to me once. Since it's on the push, it's side of the reed exposed on the inside of the accordion. Unless it has something to do with the leather on the opposite side.
I did this very carefully. I used a sturdy piece of paper thin enough slip it beneath the reeds to clean out whatever is blocking the vibration of the reed. Since there are three reeds per bass / chord I didn't feel like isolating the problem so I cleaned each one out.
It's very simple, I do it all the time but you must be careful.
There are miracles, my chirping reed was cured as I was trying to demonstrate it over the phone for another player. It is valuable to know that a bit of material can cause this problem.
Thanks for all the help.
I meant to ask, what kind of temperature was the room you played in when this chirping occured? 4 years ago when I first got my handmade (Acadian) it was ice cold coming out of the box and being naive I played it without letting adjust to room temperature. I got some serious chirps out of the thing.
The problem has fixed itself. I was trying to demonstrate the chirp over the phone to an accordion player in Chicago and it didn't chirp and hasn't since then. Go figure. There was probably something in the reed as you suggested. I live in Wisconsin and it is cool in my house, 65 or so. I have not been so foolish as to bring it in from the cold and play in a warm moist house without allowing it to reach room temperature in the case. It hasn't been out of the house since it got too cold to play on the porch. It lives in a room in the case along an inner wall away from the drafty windows with two other boxes.
Thanks for your help.