Sndio is a small audio and MIDI framework part of the OpenBSD project.

It provides an lightweight audio & MIDI server and a fully documented
user-space API to access either the server or directly the hardware in
a uniform way.  Sndio is designed to work for desktop applications,
but pays special attention to synchronization mechanisms and
reliability required by music applications.  Reliability through
simplicity are part of the project goals.

WWW: http://www.sndio.org/