Q: In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Passage: During the mid-1950s McCollum was highly busy performing as a concert soloist and performed with some frequency in operas with the New England Opera Theatre (NEOT). He sang frequently with the Boston Symphony Orchestra under conductor Charles Munch, often at the Tanglewood Music Festival, performing works like the role of the evangelist in Bach's Johannes Passion (1956). He was also a regular performer with the Dessoff Choirs under conductor Paul Boepple, performing as a tenor soloist in oratorios like Handel's Messiah (1956) and Handel's Israel in Egypt (1957). One work which he performed with frequency during these years was J.S. Bach's Mass in B Minor, which he first performed in February 1955 with the Chicago Symphony Orchestra under conductor Margaret Hillis. He later performed the work with the Boston Symphony Orchestra at Tanglewood in the summer of 1955 and with the Philadelphia Orchestra at the Bethlehem Bach Festival in 1956. In March 1955 he sang Helenus in a lauded production of Berlioz's Les Troyens with the New England Opera Theater opposite Eunice Alberts as Cassandre, Marriquita Moll as Dido, and Arthur Schoep as Aeneas.
Link Information:

In 1920, Munch became professor of violin Question: When did the conductor that McCollum sang under with the Boston Symphony Orchestra begin his career?
A:
Answer: 920