Question: How many decades has the career spanned of the musician who was commissioned to write music for NBC's national news programs
Sentence (from "Tom Brokaw"): Thomas John Brokaw ( ; born February 6, 1940) is an American television journalist and author, best known for being the anchor and managing editor of "NBC Nightly News" for 22 years from 1982 to 2004.
Relevant evidence: No