Many many years ago Mr Belt demonstrated his goods to me at my home, I was impressed and it did seem to alter the sound.  However a few weeks later HiFi News did a review and concluded the changes seemed to be related to a change in the electrostatic fields which was hitherto not seriously considered to be a factor in sound quality.  Unfortunately it also seemed that applying his products did change the sound but when they were removed, there was no noticeable alteration