
Originally Posted by
Ramako
Sonata rondo is a particular type of sonata form made to be more rondoish. Normal sonata could be characterised as
A B (exposition) C (development) A B (recap)
Sonata rondo would be
A B (exposition) A (at the beginning of development, then) C (as before) A B (recap) A (coda)
so you end up with ABACABA which is essentially a rondo form. This is just a kind of example really, and it would be best to listen to a few to get the idea. The last movement of Haydn's 101st symphony is quite famous.
Fantasia form isn't a proper form. The first movement of the moonlight sonata is 'quasi una fantasia'. It is based on improvisation, so the structure is supposed to sound improvised. A piece which doesn't conform to any set form - but sounds structured wouldn't be in fantasia form - because it sounds orderly. Fantasia form is supposed to be, wait for it, fantastic (in the sense of like a fantasy). It isn't, like many things, well-defined.