I want to know in Android it is possible to transmit modulated voice like Ultra voice changer app does during a call. I have searched a lot but I only got results for how to change voice after recording. So, please reply me that is it possible to transmit changed voice at a time of call in Android.
It seems not possible. According to this XDA-Post "The calling screen is built within the phone". You can replace a dialer, but are not able to intercept the voice spoken during a call. I cannot find any official API from android, which would make it possible to write your own "calling" App (which means record voice and send it).