There is little written evidence of what may have constituted ancient music.  The walls of the Egyptian temples however, have numerous instruments depicted on them.  From these it is clear that their music was most likely melodic in nature.  The terms ‘melodic’ and ‘melody’ mean a single melodic line, where a series of notes follow one another.  This allows the human psyche the space in which to evaluate, in a simple way, the sentiments contained in the melody.(see Danielou quote 4)
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.  

Also any descriptions in written form could easily be misunderstood by a later generation.  The oral tradition is the surest way of keeping a precious music system alive. (see Gurdjieff  quote 1)

The ancient tradition which uses melody as formulas for waking the intuition of man, has been handed down within one group or another since time immemorial. This tradition came into the 20th century (CE) embedded within the music of some Pythagorean Sufi groups of Anatolia. (see El-Kholy quote 1).

These Sufis followed the ancient Pythagorean approach which made use of the wordless language of melody.  It is because melody, of a specific kind, can transcend the intellect of Man, that it is able to bring out the pure emotions which spring from an intuitional awakening, thus providing a type of energy which allows our consciousness to be free from the attachments of worldly concerns.

From Egyptian wall painting