BTW Jason,

that diagram I posted including the text "2Hz + 4.9kHz" is just
an example of modulating a tone for a chirp or alarm

Piezos (like you find in musical Christmas and Birthday cards)
can play tunes, better suited for higher octaves of course because
of their small size. They also have a resonant frequency at which
a steady tone will be loudest. Generally around 1.5kHz - 2kHz

I started a utility to enter note pitch and duration to play tunes,
sequences and button-press tones but that's gathering dust
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