As aside about switches - its been briefly mentioned above I think, but hard switching of audio is going to
produce potentially loud and annoying clicks, since truncating a waveform is equivalent to the sound of
a sharp impact.

You need a band-limited method for cross-fading if you want live switching to work professionally (ie
click-free), which means a quality "cross-bar switch" would be a wrapper for an array of fade effects.

The same issue affects the mixer class, except that often the gain settings on a mixer are typically
ramped up and down rather than hard switched between 0 and 1. Ramping reduces the audibility
of the clicks.

In the days of analog mixing desks switching would often be done with JFETs with an RC low-pass
filter on the gate electrode to ensure switching happened slow enough to avoid clicks.