Now this habit of thought simply did not exist in Palestrina and his contemporaries and forerunners; it had not been evolved. The bit of Organum given in Figure II is hideous to modern ears just because it violates at every step our harmonic sense; it was pleasant to its composer, whoever he was, because he had no harmonic sense to be violated. To us, the sound of a tone with its fifth suggests immediately and inexorably the whole “triad” founded on that tone--root, third, fifth, and octave--and the key we consider it to be in. The sound of the tone and its fifth summons up in our imagination the whole chord and its key just as automatically as the sight of a horse’s head arouses in us an image of the trunk, legs, and tail that accompany it. This being the case, the bit of Organum quoted means for us a series of abrupt transitions from key to key, without warning, reason, or coherence. It is musical nonsense, gibberish, delirium. To its composer, on the contrary, it was merely an agreeable combination of two pleasing melodies in a harmonious interval. The chords used had for him no implications, no necessary relations, the observance of which made sense, the violation nonsense. They were pleasant combinations of sounds formed by the melodies in their progress; and that was all. Even more striking becomes the contrast between mediæval and modern usage in the more mature music of the later contrapuntal epoch. Palestrina, for example, begins a Stabat Mater as follows: [Music: score] [Illustration: FIGURE III.] _Stabat mater dolorosa,_ Here the first three chords, a modern musician would say, are in as many keys. The first is the triad of A-major, the second that of G-major, and the third that of F-major. The coherence of the passage depends, in fact, entirely on the melodies; the chords they form have no harmonic cohesiveness. For the old composers, in whose scores hundreds of such passages may be found, harmony was still a sensuous, not an intellectual or æsthetic agent. Another peculiarity of their harmonic style resulted from their attitude toward dissonances, or chords containing harsh intervals. Dissonance, as we shall have frequent occasion to see, plays an important part in modern music, both as an indispensable element in design and as a means of peculiar emotional expressiveness. In the sixteenth century, on the contrary, dissonances were admitted in the harmonic fabric but sparingly, and when admitted were subject to stringent rules, the purpose of which was to mollify their harshness. The result was not only still further to preclude the sense of harmonic sequence and coherence so essential to modern ears, and produced largely by the skilful use of dissonance merging into consonance, but also to limit the expressive powers of music to that range of feeling which is aroused by the purest, clearest, and most mellifluous chords sounding continuously, without contrast or relief.