Contrary to some popular beliefs, playing jazz is not simply a matter of musicians playing whatever they feel like. Improvisation — creating new music on the spot — is a vital part of almost all jazz traditions (see below), but it nearly always takes place in the context of some larger structure that is planned in advance. This planning can be as simple as deciding who plays what when (the order of the solos, for example) and as complicated as a completely written-out arrangement in which most of the musicians are guided by notes printed on the page. At the very least, musicians will usually decide in advance the tune that will serve as the basis for their improvisations. Perhaps another way to put this is to think of jazz as a very “free” music, one that allows players to explore a variety of means of self-expression, but that at the same time, with freedom comes responsibility. Some type of underlying organization must be in place or the result is chaos.