The PC speaker device is not a general purpose audio device, but only
capable of playing beeps. While pcspkrd does currently get built, it
never actually gets started at startup. There is also no program
anywhere inside Redox OS capable of playing any sound through pcspkrd.
And finally basically the thing it is used for on modern systems is to
emit a beep when pressing backspace in a VT while there is no input
buffered. I personally find that beep rather annoying and have disabled
the Linux counterpart to pcspkrd on my system because of this.