Conversation so far:
What did Kathleen Battle do in 2000?
In August 2000, Kathleen Battle performed an all-Schubert program at Ravinia.
Did Kathleen Battle collaborate with anyone?
In June 2001, Kathleen Battle and frequent collaborator soprano Jessye Norman performed Vangelis' Mythodea at the Temple of Olympian Zeus in Athens, Greece.

Question: What kind of collaborations did they perform?
Self-contained rewrite: What kind of collaborations did Kathleen Battle and Jessye Norman perform?