"If the challenge is beauty, Rameau is a great man; But if by random beauty of adventure is merely nature, then Rameau is small man!". In this epigram, published by the Mercure de France after the premiere of Hippolyte et Aricie, in 1733, rose a major historical question on complexity of art, giving it sometimes a laudatory value (l'Ars Nova and l'Ars subtilior "Educated man" by David Hume2, the generalized serialism and the tabula rasa after war, the school of "new complexity" - Ferneyhough, Mahnkopf, Finnissy-), sometimes pejorative (by censoring the complexity of the Ars Nova in the papal bull of 1322, the Council of Trent, "anti-élitiste et ludique" music by Carl Orff, neo-classicism, Satie, the six schools of the "Neue Einfachheit" - Rihm, Böse, Trojahn - Minimalism, easy listening, etc. ...). However, of what complexity do these artists and critics speak of? Do they admire the wealth of techniques cleverly arranged or the huge perception of the composition? Are they surprised by the accumulation of intellectually stimulating procedures, the playing difficulty or the hard work of listening with unprecedented audition habits? Complex? Complicated? Delicate? Dense? Unintelligible? Virtuous? Different? Elitist?