We were trying to do it without looking on the net but I had to look up ZZ Top since you mentioned it. I mentioned it but my buddy was adamant one of them died, but just checked and he's alive and kickin and they're all still touring. Good one etc_04.
Peter Paul and Mary is a good one too Roger. I think they would have an "asterisk" next to them because of the drummer and bassist but ultimately I would say yes since they're the main draw and are considered a trio.
It did turn out to be a harder question after eliminating a few, didn't it? Our whole thing was to see who actually had the chemistry to stick together without egos, drugs, fame, etc. getting in the way. It was pretty interesting going through them all. Thanks for your input on this everyone!