Students will enjoy learning about how the timpani are tuned by exploring the effect of the skins tightness on its pitch. With a simple home made drum, pull on the edges of the drumhead to put varying degrees of tension on it, while a student plays a steady drumbeat on it. Students can get into pairs and take turns exploring the effect of tension of skin on the drum’s pitch.
Explain how the bars on the glockenspiel, xylophone, and marimba are laid out like the keys on a piano, with a row of “white” keys along the bottom and “black” keys (chromatic tones) along the top. Students may enjoy making a “paperphone.” Cut rectangular bars of decreasing size out of colored construction paper and glue them to a posterboard or blank sheet of paper. You can then put labels on the bars.
Show the students how resonance amplifies the sound of a musical instrument. Take an individual bar from a xylophone or Orff instrument or something similar and strike it both by itself and over a a hollow tube (e.g., PVC pipe). It may necessary to have a go first with the instruments around the school first to make sure you can clearly demonstrate this using your instruments.
Check out this recording to hear some great tuned percussion: Camille Saint-Saëns, Danse Macabre. The composer gives the xylophone a prominent part at 1:45 and 3:45 (may vary slightly depending on the tempo of your recording). It is meant to convey the rattling bones of a dancing skeleton.