My daughter’s school project was to build an instrument. After toying with the idea of a drum (I am a drummer after all) and a guitar with the body of a mint tin we opted for a thumb piano.

Thumb Piano

There were many examples on the internet but many utilized an acoustic wooden box (which we did not have). For the base we tried a wooden block and a cookie tin, neither of which offered significant acoustic resonance. For the tines we tried various nails (none of which had sufficient tonal resonance) and tines from an old rake. The final components shown above are an aluminum side section of industrial cable tray for the base, two ground bars for the tine support, and nine pieces of cut-to-length 5% silver welding rods with tips rounded. The result was a resonant base and tines and a stable tine support. Oh yeah, and an A+.

Good luck with your project. Let me know if this helped.