I tried to record the voice from microphone and music played by media player at the same time (like karaoke recording). According to MSDN's description , I try to use the sample code on http://msdn2.microsoft.com/enus/library/ms679146.aspx and modfiy two parts of code for loopback mode. But it doesn't work . I record the music only. Did I miss anything when implement it? Should I set the Session GUID when call IAudioClient::Initialize()? Thanks a lot