Step 1: Split the stereo track of a loop, and render the left and right channels as separate mono .ogg loops. Activate them both as you go into the game.
Note - Each loop must be exactly the same length, or they will desynchronize as soon as they begin looping.
Step 2: Edit the events on the green button to play the left and right channel on bricks SMstereoL and SMstereoR.
Note - The brick will play the music files triggered by events that correspond to variables Track1, Track2 and Track3. The buttons, from left to right, switch to 1, 2, and 3, allowing you to set up 3 songs simultaneously.
Optional: Make a third loop comprised of the original exported traditionally, as a single mono loop, to play on SMstereoMono.
Optional: Put the name of the song playing on the gray button you activate it with.
Step 3: Stand in the center, turn the lever to Stereo, and press the green button. If you added a mono-only loop, switch the lever to Mono to compare.

You don't need this save to achieve the same effect, of course. Just make sure both tracks are activated at the same time.
People newly connecting and approaching the music bricks (unless they miraculously come in range at the exact same time) will hear dissonance.
Demonstration videoRequired add-ons for lever system:JVS Switches
Variable/Conditional Events