KMixer was removed in Windows Vista. It is replaced by the user-mode WASAPI (Windows Audio Session API) Audio Engine which is part of the revamped audio architecture. The Audio engine can operate in Shared mode or Exclusive mode. In shared mode, mixing still takes place. Pre-mixed PCM audio is sent to the driver in a single format (in terms of sample rate, bit depth and channel count) that is configurable from the Sounds control panel. WASAPI Exclusive mode bypasses the mixer, as does using third-party audio APIs like OpenAL or ASIO, which still have direct access to the hardware.
