I want to write a program which allows users to play sound clips into their microphone (recording device) so that they can mix in clips with their voice while using VOIP software (Ventrillo or Skype for example) from their PC. When I say play sound clips into their microphone, I mean the user presses a button, and the sound clip is played that both the user and the people on the other end of the VOIP connection can hear. What API functions can be used to do this on Windows?