This is the predominant reason why so much bad pop music is written. But there is a deeper wave, much deeper. It is worthwhile to know about chords, their structure and consistency and it is commendable for the beginner to learn about them as a kind of foundation and a serviceable basis of communication. Toch's book is extraordinary and certainly the finest book I've ever read about music. The essence of what he is referring to could also be called counterpoint.
Counterpoint is simply two or more melodies played simultaneously.
Peter and Marty treat their guitar playing in this fashion. In fact, The Church's entire style is basically contrapuntal. When Steve's bass lines are added then three melody lines are going together. The concept of counterpoint is interesting and the effect it has on the ear is quite difficult to describe. One listen through J.S. Bach's two-part inventions will reveal the complexity and diversity inherent in simple counterpoint.