Playing an audio file while on the call in android / send a voice prompt so that other person can hear it?

I am new to android and I have read a few blogs about play开发者_运维问答ing audio file so that other person can hear it but they are quiet a bit old. I was wondering if there were any updates/workarounds for this issue. If any help will be greatly appreciated.

Thanks in advance.

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You do not have access to the in-call audio stream from an Android application. The only "workaround" is if the device is in speakerphone mode -- what you play over the speaker can be picked up by the microphone, apparently.