Name The Year: Italy annexes Rome and the Papal States; Rome made Italian capital.?

Questions

Who wrote a collection of 24 compositions, comprising one in each of the major and minor keys, to demonstrate the benefits of the equal temperament system ?

Bach's "Die Hohe Messe" (High Mass), written during his stay in Leipzig, is known by its key signature. ?

Who wrote the words to "Der Ring des Nibelungen" ?

This son of J.S.Bach composed such works as "The Israelites in the Wilderness", "Passion Cantata", and "Solfeggio in C minor". ?

This Russian pianist and composer endured the German siege of Leningrad. ?