Sounds are caused by vibrational energy. The vibration in tuning forks is readily apparent and the sounds created can be truly beautiful. The ARC set has enough forks for each student to use one simultaneously as the class tries various activities.
Extensions reinforce the major sound concepts while using other materials.
Since sound concepts are frequently introduced as part of the second grade curriculum, shorter time periods might yield better results for these younger learners. If the children are encouraged to experiment with the materials, three 25-45 minute sessions would be useful. Draw conclusions about observations. People naturally want to hit the tuning forks on random surfaces. Students must be told and then reminded NOT to tap the tuning forks on the edges of tables or other surfaces, but always to tap the rubber striker.