The capo Captain Bob mentioned was put out by Sabine, around 20 years ago. They don't make them any more. I've still got one, and it's the best capo I've ever used. I think a lot of people didn't like them because they required a little more effort to put them on (two hands), as compared to the now-ubiquitous Kyser and Shubb capos. To me, that was a small price to pay to get a clean, even sound from a capo with little or no impact on tuning.