I've also been wondering about tuning claps. Some sounds are easier to find the "right" tune for, like metal based percussion. Claps are annoyingly hard, on the other hand. One day one pitch sounds great, another day it just seems to sound awful! Having all the elements of percussion tuned to the same note isn't anything I've been sporting with, usually I end up with some parts tuned, some parts just somewhere else, so to say. I think that helps in giving a rich and fat sound, and avoiding flat percussion in the background.

further to the above, you can tune all percussion. if you buy a drum kit for example you will have to tune your snares, and kick drum etc. all percs do not necessarily have to be in the same key. i find it difficult to tell the pitch and key of a typical hihat and kick and in many cases snares too. so i tend to tune by ear. it definitely tightens up your tune if your all your percs are in complimentary keys and your bassline sounds in line with your kicks. you can spend ages just tuning stuff though and tweaking percs.