Right - my question was about what exactly those specific things were. For example, one reason Florence became a greater centre of art than Milan was that it was ruled by a family of socialite bankers (the Medici) whose power came from wealth and prestige, rather than upjumped warlords (the Sforza) who acquired it through skill at arms and dynastic marriages. Another is that Florence had much better access to the marble mines of Carrara, and so on.

Now Mozart, Bach and Beethoven all had two generations of musicians behind them, but consider, say, Haydn. He was the son of villagers who never played an instrument in their lives - yet they recognised his talent so early that at the age of six years they managed to have him apprenticed with the choirmaster. Had he been switched as an infant with a random Marseillais or Londoner boy, his chances of receiving such an early training would have probably dropped like a rock. Was that because France and England had fewer choirs and choirmasters, both to beget little Mozarts and spot little Haydns? Because violins and spinets were more expensive? Because music was considered more of a discipline for older boys, or for girls?