A chair that is engineered so that the person sitting in will sit back on the seat is the worst kind of chair for string playing. After an hour or so of rehearsing in a chair that throws my weight backwards, every muscle in my upper back and shoulders starts to rebel, and If I cannot really put my feet on the floor, rehearsals can be painful.
Last night I was sitting in such a chair at a rehearsal in a church. I noticed that one of my fellow string players had the back legs of her chair propped up on a couple of hymn books, and she seemed not to be the least bit unhappy or uncomfortable. I made a mental note to grab a couple of hymn books for the next rehearsal. Then I thought about what might happen if me and my chair were to leave some kind of dent in the book. I definitely needed to find another solution.
I entered the hardware store in search of something useful, and I found some PVC pipe caps that were the right size. I bought some anti-skid material to stick to the top of the cap, and made a little lattice of anti-skid material over the open part, and they work like a charm. The make conventional chairs so much more comfortable.
PVC is light, so I can keep these in the pocket of my viola case. It is also cheap (always a plus for musicians), and can be decorated to go with any decor. I think I'll paint mine concert black.