Conversation so far:
Where was Pierre Monteux first a conductor?
At the age of twelve, Pierre Monteux organised and conducted a small orchestra of Conservatoire students to accompany Cortot in performances of concertos in and around Paris.
Where was Pierre Monteux a conductor for the first time?
At the age of twelve, Pierre Monteux organised and conducted a small orchestra of Conservatoire students to accompany Cortot in performances of concertos in and around Paris.
Does your article ever show Pierre Monteux as a conductor?
Yes, there are several photos of Pierre Benjamin Monteux was a French (later American) conductor.
What performance was displayed on the article with Pierre Monteux conducting?
Saint-Saëns at the keyboard, with Pierre Monteux on the rostrum in 1913.

Question: When did the performance take place?
Self-contained rewrite: When did the displayed with Pierre Monteux conducting a performance take place?