Altmann tube-o-lator lacquer is a coating-compound that you can rub on semiconductor chips found in devices such as CD-players, DVD-players, Preamplifiers, or Power-Amplifiers. And somehow this coating will change the way those chips process sound. Whereas before the sound was cold and harsh, after rubbing a bit of tube-o-lator lacquer on, the sound is warm and rich. The tube-o-lator website states:

The ALTMANN “TUBE-O-LATOR" lacquer is applied only on the top surface of plastic semiconductor packages of AD-converter-chips, DA-converter-chips, OP-amps and discrete transistors. After application, the overtone spectrum of these active devices changes immediately and permanently. The new sonic signature will be natural, full and tube-like. The ALTMANN “TUBE-O-LATOR" lacquer electromechanically balances the resonance-spectrum of the plastic chip package and semiconductor itself in such a way, that a natural sounding overtone- spectrum of the treated active device will be generated.

Why would rubbing a bit of lacquer on top of a semiconductor chip have any effect on the sound quality? The tube-o-lator people are disarmingly honest. They have no idea:

We are not able to provide an accurate description why the "Tube-o-lator" stuff actually works. Maybe some of you guys out there will solve this mystery and tell us.

Not being an audio engineer, I don't feel qualified to state definitively that this stuff couldn't work. But I can't imagine why it would work. Anyway, it's no longer for sale (demand must have been too high), so it's not possible to get any of this to test it out.