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?

That is, Germans and Austrians (and those influenced by them) wrote the history of music

This is, of course, a fully general counter-argument: any time someone points to a cluster, you can say 'well those and those influenced by them wrote the history so of course we see a cluster'.

For those who don't accept this fully general counter-argument, Murray considered precisely this national/linguistic argument about bias and examined sources written in a foreign language - eg. what did the Japanese textbooks have to say about German music? He found that this corrective did change rankings and scores... for literature. pg 486:

Histories and biographical dictionaries of Western literature are much more affected by the language of the author than are sources for Western music art and visual art, and for an obvious reason. To repeat the point made in Chapter 5: A German can listen to a work by Vivaldi as easily as he can listen to one by Bach, and an Englishman can look at a painting by Monet as easily as one by Constable. The same cannot be said of literature, because of the language barrier. German historians of literature give markedly more attention to German authors than others, English historians to English authors, and so on. It is not just a matter of national chauvinism. Spanish historians of literature give more attention to New World literature written in Spanish than do historians of other nationalities.

To quote his longer discussion in chapter 5:

National chauvinism within the West remains a problem. Works purporting to cover all of the Western world are skewed toward the nationality of the author. For example, British art historians tend to give more space to Constable and Turner than Italian art historians do, and French historians of philosophy tend to include French thinkers that hardly anyone else mentions.

An examination of these tendencies reveals that the effect of chauvinistic tendencies is minor to begin with and eliminated if the sources come from a mix of nations. Therefore the inventories for the West (visual arts, music, literature, and philosophy) employ sources that have been balanced among the major European nations (Britain, France, Germany, Italy, and Spain) plus the United States and a scattering of other nations ( Japan, Argentina, Denmark). A number of the compilations are also the product of multinational teams. Examination revealed that the effect of chauvinistic tendencies for most of the inventories were minor to begin with and eliminated by using sources from a mix of nations. The exception was literature. A German can listen to a work byVivaldi as easily as he can listen to one by Bach, and an Englishman can look at a painting by Monet as easily as one by Constable. The same cannot be said of literature, because of the language barrier. German historians of literature give disproportionate attention to German and Austrian authors, English historians to English and American authors, and so on. The selection of significant figures and computation of their index scores were therefore based exclusively on sources not written in the language of the author in question (e.g., Thackeray’s selection as a significant figure and his index score are based exclusively on sources not written in English).