libaio is a simple, high performance digital audio input-output abstraction layer; intended to be crossplatform and extremely light weight. It is less than 21K compiled and stripped on the author's testing systems.
Included is mpaio, a port of Robert Leslie's excellent madplay mp3 decoder, adapted to use libaio effectively. Modifications include realtime scheduling support, lock-step hardware buffer operation, and a special lightweight byte reordering routine.
I believe it to provide, in combination with libaio, theoretically optimum delivery of the stream to the local sound hardware.
Presently, this software is only tested on Gentoo Linux, and has only an ALSA driver. Other support is pending feedback of interest.