The conductor Stokowski was co-conductor of the San Francisco Symphony Orchestra.  He was rehearsing his own orchestration of Mussorgsky’s Pictures at an Exhibition.  The orchestra, however, was used to playing Ravel’s exuberant orchestration. Charles O’Connell recalled:

“In the midst of the rehearsal, one of the second violinists busied himself practising the Mendelssohn Violin Concerto, which his colleagues could hear but in the great orchestral tuttis Stokowski apparently could not.” Finally, Stokowski noticed some disturbance and stopped the group, but the mischievous musician, not having his eye on the conductor, went on for a few bars.  No one knew how Stokowski was going to take the situation.  Stokowski rose to humor and to every to everyone’s surprise said suavely, “There, gentlemen, is the kind of enthusiasm I want.”

Chasins, Abram (1979) Leopold Stokowski.  London: Robert Hale, p. 207-8.