Sndio
sndio is the software layer of the OpenBSD operating system that manages sound cards and MIDI ports. It provides an optional sound server and a documented application programming interface to access either the server or the audio and MIDI 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. Features The audio and MIDI server is the main component of sndio. It aims to fill the gap between programs requirements and the bare hardware as exposed by operating system device drivers. This includes: perform re-sampling and format conversions; for instance to allow a program that requires 44.1 kHz sample frequency to use a device that supports 48 kHz only. mix and route the sound of multiple programs; this allows multiple programs to use the audio device concurrently. split an audio device into sub-devices, for instance allowing one program to use the front speakers and another program to use the rear speakers as they were independent simple stereo devices. allow one program to record what other programs play. control the volume. route audio and MIDI data through the network; this allows programs running on one