The Blue Man Group playing the drumbone, an excellent example of an instrument students can create.

Blue Man Group (Official Website)
Blue Man Group

Student groups study sound and then create an instrument similar to one used by the Blue Man Group that demonstrates their knowledge of sound.. The instrument must have at least five notes of different pitch. Students must create a song using their instrument. In addition, they should write a description of your instrument that describes how they have changed the pitch to create different notes. In their descriptions, they should...
    • Name their instrument.
    • Tell whether they’ve changed the length or thickness of the vibrating objects.
    • Describe how that change affected the frequency of each note. For example, they could rank the notes from highest to lowest frequency.
    • Finally, tell how the different frequencies affect the pitch of each note. For instance, they could rank the notes from highest to lowest pitch.

Below are some more of the instruments. Obviously, students won't be able to create some of them, but with some imagination, they should be able to create instruments that approximate them.