In a crowded room with many people speaking at once, it is not easy to gather information from more than one conversation at a time. The way our mind works is to focus on one line of conversation in one period of time. This is clear when language is involved and is basically the same with music, if we wish the melody to feed us with its message. When several notes or melodies are being played simultaneously, the simple effect of a single melodic line is lost. The knowledge of his fact was natural and spontaneous to ancient peoples, especially where their melody was used to benefit the psyche of their musicians and audiences.
The lack of written evidence about how the Egyptians made their music is itself evidence that they kept their music system within a robust oral tradition, which did not require the teaching of it to be put into writing. Music, by its very nature, cannot be accurately depicted in a visual way.