What is the diffrence between a fugue and a canon?
Both employ imitation, that is, there is a theme which is stated in one voice, then other voices join in in series with the theme. The canon tends to follow a strict structure of imitation throughout the entire piece. Fugue is much freer. It also employes a theme, or subject which is announced, but the first imitation is usually in a different key (usually the dominant key). Then other voices enter with the subject in the original key or related keys. Then the subject is treated to development in segments called episodes where a fragment of the subject can be heard and sent through many different keys. The fragment might be inverted or expanded, etc. At the end, the subject is restated back in the original key and there it can close after a short coda. I have studied fugue and found it to be very open and flexible rather than rigid. Bach is said to have improvised fugues on demand! I’d love to see someone do that.
