3M Sound Damping Foil Tape

There is a product called dynamat that I used when I was into car audio, 25 years ago, that would fit your needs. Dynamat is an excellent product and easy to work with. Good Luck.

I have heard of people using tape like this...just be careful where you put inside your CD player...make sure the tape does not get too close to the tray which can sometimes get stuck on the tape.

I seriously doubt anything that thin and inexpensive is going to beneficially affect the resonant properties of your mdf shelving. That stuff is designed to dampen vibrations in metal air ducts, a completely different material and application. For damping the insides of components, get something designed for the job like this 3M material:

http://www.musicdirect.com/p-205-audio-additives-3m-damping-sheet.aspx

I have used material like this in cd players. If the cd player has inadequate damping and vibration control, it can (but might not) help to tighten the focus and resolution of playback.

Using these products on the shelving your gear is on should be fine. The main concern would be blocking the air circulation that flows around the components.

Putting products like these inside your gear can cause overheating, shorten its parts life. Worse yet, a safety hazard. All of our audio gear dissipates heat. A lot (possibly all of the heat) of this heat is dissipated through the metal cabinet itself. When you put some of these products inside of your components, can also lead to thermal runaway type of situation. You need to know what your doing.

If you don't have any temperature measuring devices to check the running temp of the unit running continuously before, and after installing these products, it can be even more risky.

I also use a product called Dynamat at home and in car audio, and similar products by other names, ( Blue Tac, U.S.C. ). A very useful butyl based product when used in the right application. Be a little cautious it's not easy to remove completely.

Thanks for all of the responses. I started my search for this material with the intent of applying it to the MDF shelves of my DIY rack. I have also heard of some mods to electronics that included applications like this, but this is not my first purpose for seeking this. I will try it on the bottoms of the shelves and see how it goes. Not very expensive stuff, so the risk is low to try it.