I'm splitting this question off of When was beeping invented, in a user interface sense? because I think it's more answerable on its own and I suspect likely to still be computing-related.
At some point in the past, all electrical switches would have provided only natural/"real" feedback. The physical mechanism of the switch itself would click or clunk or rattle or thud. Some switches were intentionally designed to incorporate e.g. tactile domes or other mechanisms to make this feedback more pronounced, and I suppose other switches could have been designed oppositely for quiet/unnoticed activation.
But eventually switches weren't just controlling simple electric loads directly but had additional electronics in between or instead. This correlated with — and probably even caused! — buttons becoming smaller and less physical, since they could now switch circuit-level voltages instead of load-level currents. With something like a cheap momentary switch or elastomeric keypad or membrane keyboard there is very little physical feedback and it is ambiguous whether/when the button is actually pressed. So it became fairly common for an electronic device to include additional logic/circuitry to give a little "beep" sound to confirm for its user what a physical "click" or "snap" would have provided from a different style of switch.
What was the first user interface that used an auditory beep solely to confirm that a button had been activated? (Things like telegraph keys or car horns or musical instruments don't count since making the sound itself is the purpose of activating the circuit.) Was this kind of feedback part of a computer or microcontroller system or did the idea happen already in the days of analog or basic digital circuitry?
