Non-immersive perspectives in virtual environments enable flexible paradigms of perception, especially in the context of frames of reference for conferencing and musical audition. Traditional mixing idioms for enabling and disabling various audio sources employ mute and solo functions, that, along with cue, selectively disable or focus on respective channels. Exocentric interfaces which explicitly model not only sources but also sinks, motivate the generalization of mute and solo (or cue) to exclude and include, manifested for sinks as deafen and attend (confide and harken). Such functions, which narrow stimuli by explicitly blocking out and/or concentrating on selected entities, can be applied not only to other users' sinks for privacy, but also to one's own sinks for selective attendance or presence. Multiple sinks are useful in groupware, where a common environment implies social inhibitions to rearranging shared sources like musical voices or conferees, as well as individual sessions in which spatial arrangement of sources, like the configuration of a concert orchestra, has mnemonic value. A taxonomy of modal narrowcasting functions is proposed, and an audibility protocol is described, comprising revoke, renounce, grant, and claim methods, invocable by these narrowcasting commands to control superposition of soundscapes.

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