He served seven years as an apprentice in an organ-building firm in Edinburgh, where he learned every phase of pipe organ construction.
At the height of its operation in the 1920s, the company had branch offices in New York City, Detroit, and Hollywood, and employed some 375 people.
[2] Marr was awarded a U.S. Patent (Number 1,762,274) in June, 1930 for "...an organ having an improved stop mechanism of such character as to make it easy for any organist to quickly select and render the correct tone colors for any desired musical action, mood, or emotion.
[5] The onset of the Great Depression in the early 1930s, combined with the advent of "talking pictures" (movies with soundtracks), meant that sales for the Marr & Colton Company began to decline drastically.
[2] In 1932, John Colton left the firm to join the Kilgen Organ Company in St. Louis as a salesman, and died shortly after.
David Marr set up a shop in his home cellar and garage, performing organ repair work.