At the National Museum Of African-American History & Culture in Washington, DC, the music room displays artefacts from some of the greatest talents and music genres that America ever nurtured, from Duke Ellington to the hip-hop movement.

In one corner of the room, you’ll find a framed annual royalty statement from December 1, 1967, as sent to New York-based composer Hall Johnson by G Schirmer, one of the oldest music publishers in the USA (now part of the Music Sales ...