Abstract: The disclosed invention constitutes a method and system, including an audio mixer, for selecting audio streams from one or more applications running on a computer system. An application can register its audio streams with the audio mixer either as sound focus audio streams or as priority audio streams. With respect to the sound focus audio streams, the audio mixer determines which of the applications has the sound focus and generates an audio output signal from those sound focus audio streams to drive the computer's sound device and thereby to produce an audible sound for the user. Sound focus is determined when an application gains the input focus, opens an audio stream, closes an audio stream, or registers with the audio mixer. With respect to the priority audio streams, those priority audio streams are always selected by the audio mixer and are mixed with the sound focus audio streams from the application having sound focus to generate a composite audio output signal.