How to build an instrument for physics cl?

I have to build an musical instrument and play a recognizable song in front of the cl on it. The instrument has to be able to play an octave, and be tuned. (So, no percussion instruments like a drum.) Does anyone have any good ideas? I'm looking for something easy to construct, since I really am not good at difficult projects that involving building things. Any good websites with instructions for constructing the instrument would be very helpful!