Meredith and I plan to create an acoustic, gravity-driven, two-person musical interface centered around different types of balls falling into a resonant bowl.
Containers holding several different types of balls - i.e. marbles, wooden balls, metal balls, rubber balls, etc. - will be mounted in a circle around the top of a pole. The containers will be closed by default but will be able to open to let one or more balls out when a string is pulled.
On the ground next to the pole, there will be a resonant bowl - preferably clear - to catch the balls as they're released from their starting containers. To play the instrument, one person would turn the handles to change the position of the containers to align them with the bowl, and one person would pull the strings to allow balls to fall into the bowl.
The sound would be produced by the different balls, made of different materials, falling into the bowl. As the bowl fills up, the sound should change. While pitch and timbre depend on these somewhat unpredictable factors, the users -- whether one or two people at a time -- are in charge of the rhythm.
Once all of the balls had fallen into the bowl, the balls would be poured into some sort of mechanism that would sort them into their various types to be returned to the individual containers.
We see the sorting process as part of the performance. We also predict that the instrument will be messy. The faster and more furiously you play, the messier it should become.