ENO is an audio server designed to make it easy for applications in the Unix environment to incorporate non-speech audio cues. At the physical level, ENO manages a shared resource, namely the audio hardware. At the logical level, it manages a sound space that is shared by various client applications. Instead of dealing with sound in terms of its physical description (i.e., sampled sounds), ENO allows sounds to be presented and controlled in terms of higher-level descriptions of sources, interactions, attributes, and sound space. Using this structure, ENO can facilitate the creation of consistent, rich systems of audio cues. In this paper, we discuss the justification, design, and implementation of ENO.