It was habitual among Stevenson's family, friends and biographers to make such supercilious statements about his music. But musical facility should never be confused with musical ability. Berlioz played the flageolet, too, and never mastered it, while Beethoven's piano playing deteriorated as he produced his greatest works.
A simple examination of the facts will decide the question of Stevenson's musical ability.
He wrote more than 120 pieces, almost 1/3 of which were original. His compositions consisted of songs, dances, instrumental works, counterpoint exercises and at least ten pieces that used piano. He wrote in 19 different keys, including five modes. Using six different meters he wrote at least 65 solo pieces, 27 duets, 14 trios and two quartets for various combinations of flute, flageolet, clarinet, violin, piano, guitar, mandolin and voice. He frequently transposed pieces and knew how to modulate from one key to another. He played piano, Boehm flageolet and penny whistle.
Never having studied music or any musical instrument as a child, and never having studied music formally in any way as an adult, he accomplished all this in about six years.
This is not a description of someone who had "failed to master the rudiments" and whose "knowledge of music was not very profound."
It should also be noted that during those six years he took enough time off from musical composition to write 17 major works of English literature, including Kidnapped, Dr. Jekyll and Mr. Hyde, and A Child’s Garden of Verses.
In defense of Louis's playing, it must be said that the flageolet is not the best instrument for someone afflicted with tuberculosis, as he was said to be. More than any other orchestral instrument, it requires skillful breath control to play in tune and to produce a pleasing tone. This is even more true of the Boehm flageolet