Move your PC into the bathroom . <| sep |> Ok , short , easy answer , without scientific jargon , because I ' m not one . I know this is basically right , though . Quality crystal glasses resonate at a predictable frequency when agitated . So , if you wet your finger , and run it over the rim , the friction between your skin and the rim of the glass makes noise , just like when you smear your finger against a clean dish , and it makes a noise . Since crystal resonates predictably , you can take a glass of a certain size , fill it with a certain amount of water , and get the same tone doing that , every time . You can adjust the pitch of an individual glass by adding or removing water . So , the quick notes , they are quickly and briefly running a ringer along a small portion of the rim . The longer notes is where you see them circling the rim for a second or so . Note , this doesn ' t work with every glass , or at least not very well . It has to be decent crystal glasses , preferably wine glasses or large brandy snifters . Btw , if I got any of that wrong , and someone has a more accurate answer , pretty please correct me .