His attempt to reconstruct the musical scale was afterwards overshadowed by the system invented by Guido d'Arezzo, and it is therefore unnecessary to describe it in detail. His great contribution to progress was the discovery that more than one sound could be played or sung simultaneously, thus creating a composite sound, the effect which we call a chord. However, in deciding which sounds should be allowed to be played or sung together, he was influenced partly by the mysticism of his age, and partly by a blind adherence to the remnants of musical theory which had been handed down from the Greeks. As Franco of Cologne, later (1200), in systematizing rhythm into measure, was influenced by the idea of the Trinity in making his
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time tempus perfectum, and adopting for its symbol the Pythagorean circle
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, so Hucbald, in choosing his series of concords or sounds that harmonize well together, took the first three notes of the overtones of every sonorous fundamental, or, to express it differently, of the series of natural harmonics, that is to say, he admitted the octave and fifth:
