Oh, that does bring up another point... If you have a group of musicians that all play by ear, all you get is a group of improvisations to your music that they heard. If you have a group that reads, it can be led as a single entity to one final musical goal that is written down and guided by one person's intent. This performance can then also be shared and played in the same manner by others.
Another advantage... the vast majority of people that play by ear never play a song EXACTLY as they heard it and over time that music changes. That music that you created on the fly has very little chance of surviving integral for more than 1-2 "generations" before changes are introduced... unless written down. Kind of like having 10 people in a room and each person whispers a phrase to the ear of the person next go them. By the 10th person, that original phrase has changed entirely, possibly several times over, losing all the intent and meaning that the first person originally "created".
One may create something new but there is no way to preserve it or assure consistency without being able to write it down. I also don't believe that any system is so restrictive that someone could create any form of music that could not be preserved via notation.
All original work starts out as thought, but if none of it is saved unless recorded in one form or another, via notation or a less accurate manner, listening to a recording done by the original artist and accepting the variations that the listening artist will invariably introduce over time.
The value of being able to read and write music can be answered by asking one simple question;
Of all the great artists that ever lived, how many original works that were ever created and not placed in notation due to the inability to read or write music, have survived the test of time in their original form? The answer is... unless this task was passed to someone else that could read and write music... none survived.
