William, I found your comment about Bach interesting.
At the time of his death, Bach's sons already viewed "dad" as being passe. All those glorious notes were silent. It was not until Mendelssohn rediscovered J.S., that his music again took flight, and eventually became heard around the world.
As for creating music by manipulating timbre, if one is not careful, one can accidently throw out the entire world of jazz, a musical form that makes much of timbre. Granted, to be a fine jazz musician requires far more musical knowledge than simply being able to turn dials and knobs (Note: it is also interesting that Wendy Carlos started turning dials and knobs creating timbres to use with the music of J.S. Bach). The point is simply that - though stating the obvious - significan musical forms exist that emphasize something other than paper and pencil.
IMO, it takes considerably more musical knowledge to create tonal compositions that say something than to write atonal whatever. With the atonal music harmony and counterpoint do not have to "work". During my college days, I learned far more about atonal concepts (even though not studying composition), than I would ever end up using, or wanting to use. For my interests, one of the subjects I really wanted to learn about was 18th century counterpoint. I took the class, but the professor spent most of his time - when he was there and the class actually met - talking about 20th century atonal and electronic techniques. I went in knowing nothing about 18th century counterpoint, and came out knowing nothing about 18th century counterpoint. Since it was a passe, "old" technique, that type of counterpoint simply wasn't necessary. I could write all the atonal stuff you'd never want to hear, but a fugue that actually worked, and worked well... no.
To me, it takes far more technique to write traditional tonal music that says something (thereby generally excluding a certain film "composer" and his legion of clones) than the atonal forms. I do wonder how many composers had educational experiences similar to mine - where they simply were not taught the basics of traditional technique (self-study then becoming the option). One wonders how much of what is going on today relates not so much to lack of ability, but to basic ignorance. Throw in the demands of the culture, directors, et al, and the situation is far worse. But, if composers no longer have the writing skills, chaning the situation will be even harder.