Use the command like this:
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./dist/build/tonesynthesizer/tonesynthesizer <file-name> <tempo> | aplay -t raw -f U8 -r 16000

the program will generate the byte stream, which pipe'd to aplay will be heard by you :)

<filename> is the name of the file containing the notes to be played. <tempo> is in BPM.
This file has the following format:
<note>, <note>, ...

Where <note> is like:
c, c#, d, d#, ..., b, c', c#', ..., b'