I remember an old 1401 progrm that when running would cause a small transistor radio placed on top of the computer to play a ‘tune’ of the varying electrical pulses generated by the computer.
Only a computer running a single simple program could do that. If the program was run on a computer capable of doing more than one thing at a time, the effect was no longer possible.
We did the same thing with our IBM 1130! Ah, the good old days.