Play Audio File during an outgoing/incoming call i

Question

I am thinking of developing an application which will act like an IVR so when the user calls a number and does not want to talk instead he/she wants the called up number to listen to a pre-recorded sound. A sound will be played and called number will hear that.

I have tried searching for any thread which could have discussion about this however did not find anything. I know how to record a sound but I don't know the procedure to play the same in a phone call.

One work-around I can get that to put the speaker phone on and play the audio using MusicPlayer however that does not full-fill my requirement.

I don't want speaker to be used.

I followed these URL, and some of them said it's not possible. Is it true?

Link 1

Link 2