This is very unpleasant to modern ears, yet it is not quite so bad as a series of fifths. When Hucbald wished to write in four parts he simply repeated the two treble parts in the bass an octave lower. And when he wrote in three parts he simply "doubled" the lower note of his fourth or fifth in the octave above, which is a process also forbidden in modern part writing because it makes two parts the same in melodic progression. Hucbald also employed a form of harmony in which the lowest note always remained the same. This was what we now call a "drone bass," such as is heard in the bagpipe, and it was certainly more flexible than the other kind because it admitted of the use of other intervals than the fourth and fifth. But the idea of writing in more than one part, once having appeared in music, developed itself gradually. All the earliest harmonic combinations sound ugly to our ears because of the difference in the character of the old scales adapted from Greek music for the Church and that of our scale. If the harmonists of those early days had been using our scale, no doubt they would have discovered how to write fine chords. They did, in the course of time, hit upon some of the combinations now used, and so the foundations of modern harmony were laid. But the modern style of writing did not come into use for several centuries after Hucbald's time. The next element of music which made its appearance was rhythm. This came about through the improvements in notation and the practice of singers. It seems that after learning to add a second part to the _cantus firmus_, or chant, the singers, who were acquiring considerable dexterity in their art, began to ornament the additional part. This addition of ornaments was called the art of descant, because it was descanting upon a given theme. The singers all took to it with delight because it gave them fine opportunities for the display of their voices and of their musical skill. In some parts of France and the Netherlands this practice became a sort of mania. The voice which carried the chant was called the tenor, from the Latin _teneo_, "I hold." The other voice added an ornamental part _above_ the chant, and as there was no measure in music, the two parts seldom came out together at the end. As long as the voices had moved in parallel fourths or fifths it was not difficult for them to keep together, but with the descanter singing two or more notes to every one of the _cantus firmus_ it was quite impossible for them to do so. No one knows just when this art of descant entered into music, but it is certain that it was known some time before the close of the twelfth century, for it was about then that Franco, of Cologne, made successful attempts to systematize notation, and in doing so regulated the measure of music.