In the growth of modern music the second step was the introduction of harmony. The simultaneous sounding of notes of different pitch in combinations called chords is so essential a part of the music of to-day that even the uneducated mind has difficulty in conceiving a tune as wholly dissociated from the coloring influences of its harmony. Every schoolboy is accustomed to hearing melodies with what he calls a "bass" (an accompaniment founded on chords), and in the commonest music-hall songs the familiar harmonies are the results of centuries of experiment among the ecclesiastical fathers of modern music. It is difficult for us to understand that there was a time when harmony was unknown to musicians, but such is the case; and the first experiments resulted in the use of combinations which sound intolerable to our ears, while some of those which we regard as the most familiar and useful were deemed unbearable by some of the early authorities. For example, no modern chord can be formed without the third, _i.e._, the third whole note above the key-note. In the key of C that is E; in G it is B, thus:-- [Music: Two Note Chord] Yet for several centuries after harmony began to be employed that particular combination was forbidden, so that it was impossible to write the common chord of C major [Music: Three Note Chord] or of G major [Music: Three Note Chord] or of any other modern major key. The result was that for several hundred years music developed along lines not those of chord harmony, the first rude experiments at which early gave way to what is called counterpoint. What that system was we shall see in good time, but we must now give our attention to the early attempts at harmony.