Conversation so far:
Who is Frank Rich in relation to Stephen Sondheim?
On April 28, 2002, Stephen Sondheim and Frank Rich of the New York Times had a conversation.
What were the conversations between Stephen Sondheim and Frank Rich about?
In connection with the Sondheim Celebration, Stephen Sondheim and Frank Rich of the New York Times had a conversation.
What was the Sondheim Celebration in 2002 for?
The Kennedy Center held a Sondheim Celebration, running from May to August 2002, consisting of six of Stephen Sondheim's musicals.

Question: Which musicals?
Self-contained rewrite: Which musicals were shown in the 2002 Sondheim Celebration?