here is a few fairly simple ideas for creating music lesson plans about percussion instruments.
To help students understand how timpani can be tuned, demonstrate the effect of membrane tension on pitch. With a simple home made drum, you can often vary the tension of the skin by simply pressing or pulling at the edges of the skin, while another student hits the drum in steady rhythm. If the students have their own drums, pair them off and let them take turns repeating the experiment you just demonstrated.
Have a look at the keyboard percussion instruments, the xylophone, marimba and Glockenspiel, and show the students how they are laid out just like a piano. Have students make a “paperphone.” Cut rectangular bars of decreasing size out of colored construction paper and glue them to a posterboard or blank sheet of paper. Label the bars with the appropriate note names.
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). You will likely need to experiment with bars and tube size before finding a combination that resonates well.
Recommended listening: Béla Bartók, Music for Strings, Percussion, and Celesta, III. Adagio. This movement has prominent parts for xylophone and timpani. The timpani performs glissandi throughout, an excellent demonstration of its pitch capabilities.