Are there norms in free improvisation? A better question might be: are there rules? Free improvisation has been called many things--instant composing, non-idiomatic improvisation, spontaneous ...
The birth of art : up to 500 BC -- The art of power : 500 BC-AD 1000 -- The blending of cultures : 1000-1300 -- A new beginning : 1300-1500 -- Perfecting the art : 1500-1600 -- Past and present : 1600 ...