Playing music in background during a call

Hi, I am trying to play music in background while making a call. So I mean that while speaking I need ability to play music in background using buzzer(main speaker) ,so the another person on the line could hear the music from the speaker. I have been studying Android API , but didn't find anything, that allows me to do this. I have tried services, but this also doesn't work.
I have found similar questions but there is no any solutions. Also I don't need ability to hear person on the other end of line, so I don't need to use earpiece(speaker). I need to use only microphone and buzzer(ringer).
Is there any way to do this using default API . Or there is no such feature at all available on Android Platform. Maybe there is any way to do this using native interface and system calls or something else. or at worst to modify ROM or Android OS or Kernel.
I don't need really solution(it would be great of course) in code , I need just direction where to start. Maybe there is easy way to do this , so I don't want to reinvent the wheel.
I would be grateful for any answers and suggestions about this question.