Baumol and Bowen pointed out that the same number of musicians is needed to play a Beethoven string quartet today.

http://en.wikipedia.org/wiki/Baumol%27s_cost_disease

The original study was conducted for the performing arts sector.Baumol and Bowen pointed out that the same number of musicians is needed to play a Beethoven string quartet today as was needed in the 19th century; that is, the productivity of classical music performance has not increased. On the other hand, real wages of musicians (as well as in all other professions) have increased greatly since the 19th century.