A melody is played on a single string, sung by a single voice.
While harmony requires several strings, it implies the participation of several voices or several instruments, the combination of which is a whole science.
Thus, melody is closer to the heart, to feeling; harmony is more linked to the intellect, to thought.
But neither melody nor harmony is complete in itself, for they do not touch the whole being. To reach perfection, they must be able to rise to the realms of the soul and the spirit; this is the domain of the symphony.
The heart, which speaks in the melody, must awaken the soul, and the intellect, which expresses itself in harmony, must awaken the spirit.
The soul and the spirit represent the feminine and masculine principles, but manifested in higher realms.
So you see how clear these analogies are:
Melody (the heart) and harmony (the intellect) must rise to reach the celestial realms of the symphony (the soul and the spirit).
It is in the symphony that humankind can truly flourish, because it touches upon the cosmic dimension of being.
The symphony represents the entire universe singing in unison: the music of the spheres.
Omraam Mikhaël Aïvanhov – Spiritual Alchemy, Chapter VIII.