[mrighele]

Theoretically, an RTOS improves the quality by ensuring that the audio subsystem is fed cpu time and data with enough granularity that there is no interruption or delay on the sound stream (no "buffer underruns") and there are no glitches on the output.

In practice this should not be an issue if you are just playing music (at worst, add some more buffering) but it can be if the music must be synchronized with something else and you need low latency AND the system is busy doing also something else.

I found Linux in particular to be surprisingly bad at this when mass storage is involved (copy files on a spinning disk, somehow playback of audio from an SSD is affected... why?), although low-latency versions of the kernel help in that regard.