I would like to play a sound file during a phone call so that the person at the other end of the line can hear it clearly.
I know it is possible to play sounds on t
I very much doubt it is possible.
A telephone is an emergency communication device. The inability to make, receive or even clearly hear a phone call could literally kill someone. Consequently, the iPhone API strongly protects the integrity of the phone before all other functions.
Even if you did figure out a way, I doubt Apple would let it through. (Think of the liability issues for them and you!) The iPhone isn't a very small laptop, its a phone with a computer attached and the phone comes first.
You should always consider that when starting a design.