Page:Letters to a Young Lady (Czerny).djvu/67

 We can, as you see, form from these chords innumerable passages, and even entire melodies, while the harmony on which they are founded always remains the same. And it is the same with all the other chords which are practicable in music.

A composer must have studied thorough-bass well; as otherwise he would, in every composition, entangle himself in irregular, and therefore irresoluble, discords. And, even to the player and practical musician, this science ought not to remain unknown; for it is equally useful and pleasant to be able to account to oneself, as to how far each composition may justly lay claim to intrinsic merit; and because thorough-bass is of the greatest assistance in extemporizing, playing at sight, and accompanying.

But before we learn to know the chords, we must see from what they are constructed.

Each chord must consist of at least three notes, sounded together. When we strike only two notes together, it is not a chord, but merely an interval.

There are ten such intervals in music, which here follow; C being always taken as the lower note or root.