At one point it was. You could even record the sound on a handheld recorder and play it back. But it hasn’t worked in a long while. Pay phones mitigated this in a low tech way - by software muting the handset.

Edit: oh yeah, and after that, you’d just call the operator and tell them the keys were sticky and to dial the number for you, then you’d “insert the coins” by playing the tones.

Well, or you just third party billed the call to someone you didn’t know. That worked too.