Calling somewhere, being put on hold for 15 minutes and up, is not very pleasant. Especially if you don't like the waiting music. Now I'm not talking about the "on hold" music people hear when they call me; I'm talking about the music I hear when I call customer service, etc.
Now as a programmer, I assume there is no such thing as a "protocol" for telephony that tells the smartphone if the user is on hold or not. But if there was, there would be a way to listen to my own music while waiting until an operator picks up my call.
But maybe someone figured out a way to make this possible? Does such app or feature exist, or is it as simple as that it's not implementable, because there is no way of retrieving information about whether or not the call is on hold?