The most important instrument when playing Capoeira is the berimbau. It's basically a single string tensioned over a wooden stick, with an amplifying gourd at the bottom. There are only two notes (altered by pressing a stone against the string) but a variety of percussive sounds possible, and it is quite tricky to consistently play even a basic rhythm - let alone sing aswell! Djanira and her father Jorge have written an article about it, which you can find here.
I recently bought a new berimbau (from www.capoeiragem.com) because the one I borrowed from Jorge had...errr...an accident. Very embarrassing. Suffice it to say that Jorge is now the owner of a brand new berimbau, which I am borrowing on a long term loan. The biggest problem is that it is bloody impossible to string the thing! It's so hard to bend the wood and I don't want to try and bend it too much because they do break :(