I'm just guessing here, but it appears that there is some harmonic vibration that occurs when the tom is mounted to the bass drum. If it were mine,
1. I'd start with the tom. Are all the tension rods under tension? Do they all have washers installed? Take a head off the tom and ensure that all the interior lug bolts are tight.....Are the bolts that hold the tom mount tight?
2. Is the little nut that secures the muffler tight?....Inspect the muffler assembly for any looseness in the several washers that are used with the "baseball bat" muffler...If you have a "round" muffler, I take a piece of wound-wire (like you use to hang a picture on the wall) and I use two needle-nose pliers to wrap the rivet underneath the muffler. Wrap it tight (like a scarf) with a few turns of the wire, cut off the excess wire, then leave the wire on it. That will eliminate any play in the muffler and remove rattle.
3. If the buzz problem remains, I'd go to the bass drum. Are the tension rods and claws under some tension?...Remove a head and check all the interior lug bolts and the bolts that secure the tom mount...and the bolts that secure the spurs.
Harmonic vibrations can drive you crazy! Good luck with this, and let us know when you find the culprit. You will....
Regards, mb