Show us all of it. I see pillow damage and dry-rot on the one pic.

Oh no! Dry rot does not sound good for drums. Here's the damage on one of the toms.

I've no reason to believe these drums were ever abused, they look like they've sat in a living room since 1970. Is there anything that can be done about any fungal damage?

Yes, dry rot is not good. It`s caused by the interior being allowed to dry out and then moisture is free to breath in and out of the wood, They don`t get wet or damp, but do expand and contract with temperature and humidity changes. If left to sit, never reconditioned, the de-lamination just continues to spread.

Yours can be repaired but it`s a long, slow process of trial and error and the use of fine wood working or dental like tools, glues ,clamps and in your case with the BD, maybe re-ring removal.

The cracking and de-laminating may only go one or two plies deep, it`s a little easier to deal with but in all, if you let it go, you get vibrations or buzzing from playing them.

Steaming can release the grip the glue has around those areas so you can lift layers without breaking, or breaking, but you can get glue under there and clamp it in place.

These repairs have been done here in this section and detailed instructions with them, you have to search around and find someone that posted such repairs. read as many as you can ,get all the info, pluses and minuses, take your time and don`t rush. Gather everything you need, and if your will is there, you can do these repairs.

We have seen much worse come back together.

It`s important to wax or treat the interior of the shells every five or ten years accordingly.

Well that's somewhat encouraging, sad that the damage has been done but good it can be repaired. But I didn't sign up for this haha!

So looking at the shells, it seems the damage doesn't go too deep into the ply. I'll look around the forum, but my first thought went like this: steam out the re-rings and rout out a thin layer of ply as deep as the rot goes. Then chemically treat the wood to kill the rot, and then install new deeper re rings to cover the routed area. Is this a bad idea? I believe the shells are 3-ply.

Also, should I wipe down the interiors (with alcohol or something) to kill rot on the surface? This is probably most needed for the bass drum.

Routers spin at very high rpm`s, without a jig,if you so much as breath too much on it, it will drive through the shell instantly. I suggest soaking the areas with water based Elmer`s wood glue on a paint brush and maybe force it into cracks with a blow dryer set on cool or thin flat knife or dental picks. put tin foil on a strap piece of wood and clamp it around the perimeter with many clamps. Like ten or fifteen screw type so you can control pressure. The squeeze out can easily be removed after. The foil is so the wood glue don`t glue your clamp strap in place.

You can`t kill the dry-rot, it`s a symptom, but the mold and mildew can be killed with Clorox and water solution.(wipe it on) Laundry bleach kills mold and mildew on contact. Let it sit a few minutes and it will lighten the stain as it dries out. Looks like that has already been done on the BD stains. Bleach does not damage wood but will lighten it up. It works as it dries out.

Go to it and post progress and ask questions,...like I said, much worse has been corrected.

The first picture (bass drum) looks like water damage. Please post some additional pictures showing the entire damaged area. It is hard to tell if this is a few square inches or the entire bottom of the drum. The second picture only shows a ply crack, not uncommon on 50 year old drums. Unless it is loose no action is necessary there. Some excellent wood workers here, hopefully they will respond.

That doesn't look like rot to me. It looks as though the inner ply has tried to pull away from the re-ring. maybe they got wet at some point and those plies shrunk when they dried? Either way I don't think it looks all that dire. I've seen much much worse. If it's not effecting sound, I would leave it alone.

The inner ply goes under the ring. Dry-rot is from expansion and contraction due to moisture and temperature changes and never actually gets wet. When wood gets wet, after it dries, the pulp inflates and allows the wood to breath in and out moisture it normally wouldn`t. Gone unprotected or treated, it`s like rust, it just keeps going.

The obvious damage is plywood de-lamination, solid wood cracking, shrinking and crumbling, no longer has strength to spring back (snaps) or allegation cracks.

I deal with it all the time in the Trades.

The BD damage is pillow or blanket related for sure. I see the stains on the shell. The tom tom crack is prolly shrinkage as mentioned due to age and not treated. Those can simply be filled.

The lift of de-lamination has a cavity to hold air and moisture will travel through, it will just keep going and must be repaired.

We have all seen much worse repaired.