"BX" cable would be a good choice. The wires are inside an electrostatic shield (the armour and its equipment ground wire) and the wires themselves are twisted together, one twist every 6 or so inches. This twist will cancel any stray magnetic fields from the currents in the wire. These things are routinely done with audio cables to avoid picking up external hum and noise. In this case with the BX cable, you're confining the noise and hum INSIDE the cable to prevent it from getting into the audio equipment and cables. These points are valid and not "snake oil", so have at it with your sales pitch....
To avoid "ground loop" hum problems, be sure to have all the BX grounds come from a single panel and follow a common path for the home runs, and tie all the grounds together at a single metal box in the audio room before branching to other outlets in that room. Avoid the BX touching water pipes or such.
