Signals homework: make an instrument, or make a light sensor, something like that

I tried to insert "making" in my latest go-round teaching engineering Signals and Systems.  It didn't happen - yielded one lonely drum - but I will try again before the semester ends.  I'll show the class this video for inspiration.

Because we all need to play, for God's sake.

I'll possibly give the option of using software (instead of making things), that is, options 3 and 4 will be
- to demo STKInstruments (synthetic toolkit available for instance in Chuck music programming)
- or demo Image Processing using Mathematica or a popular programming language?
But maybe it's better to keep it simple with two options only?

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