Conversation so far:
What is interesting about the Vienna Boys' Choir's recent history?
Gerald Wirth became the Vienna Boys' Choir's artistic director in 2001. However, since then, the choir has come under pressure.
Why has Vienna Boys' Choir come under pressure since Gerald Wirth became their artistic director in 2001?
The Vienna Boys' Choir has come under pressure to modernize and has faced criticism of their musical standards, leading to a split with the Vienna State Opera.

Question: What changes did they make?
Self-contained rewrite: What changes did the Vienna Boys' Choir make under pressure to modernize?