I have one piano student who begs to play this game every week. Too often practice time can become repetitive and boring, especially for young musicians. Repetition is not a bad thing to have during practice - in fact, we need to do things correctly over and over so that we can get the muscle memory in our fingers or voices. Whether that be a difficult rhythm, melodic passage, or technical requirement.
For instance, if a child has a forte section of a piece, those muscles need practice playing forte with good technique... and they will not learn it securely just playing it one time! It takes practicing phrases of the song over and over with good forte technique for muscles to develop that habit.
However, mindless repetition can turn music practice into a very mundane and grudging task. Often when children need to focus on a specific element in their music they can become disengaged and easily distracted. That's understandable. It takes a lot of focus and self-control to work that diligently!
This simple game helps students stay focused during practice sessions when they need to repeat something so it gets better. It involves seven objects that can be placed on the piano. (I play with brightly colored paper clips.) When the student plays through the phrase keeping the element in mind (rhythm, dynamics, phrasing. . .) he or she gets to move one paper clip over to the other side of the piano. By the time all seven clips have been moved, the student has practiced that phrase correctly seven times. I find that without the tactile motion of moving an object from one place to another, students brush over some of these important focus elements when they practice.
Another option some people like is to use things like skittles or m&m's instead of paper clips.... Each time the child plays the phrase he or she gets to eat one candy. As you might imagine, kids like this version of the game quite a bit!
It doesn't matter so much what objects you use. This game is a great way to help students stay focused while working on short term goals in their music.