I pulled out Empty Ed last week.  I have not used it for a couple years and I had forgotten how much the children enjoy it.  If you haven't tried it her are the instructions.  It's simple.

Take a empty pickle jar, or a clear container.  Attach a frowney face to one side and a smiley face to the opposite side.  Introduce Empty Ed to the children and tell them that ED is sad (only show the frowney face) because he is empty of the warm fuzzy feeling (cotton balls) he gets when he hears beautiful music.  So to help fill him back up the children need to sing their very best. 
 

In junior I was the judge.  If they sang their very best I chose a child to come up and put 10 cotton balls in Empty Ed.  If I thought they could sing it better I told them, "that was worth 7 cotton balls, let's sing it again and see if you can make it 10".  In senior I chose three children to come up and be judges.  They each had 3 scorecards with 1, 2, or 3, written on it.  At the end each judge held up one number depending on how well they felt the song was sung.  We totaled the 3 scores and added that many cotton balls to the jar.  At the end when Empty Ed was filled to the top, I turned the jar around to the smiley face and congratulated the children on bringing the joy of music back to Empty Ed.