This video shows how I produce the sensor buttons from chicken mesh. The sensor buttons (96 pieces altogether) will be attached to the inner sphere
shell. When touching two sensor buttons which are next to each other, an electric contact will be established. Using sensor circuits, each of them will trigger one of the 48 sound generators.

chicken mesh was the cheapest and easiest material I could find. In addition to that, it is quite lightweight. The buttons can be attached to the steel frame without further difficulties, just using cable zip-ties.