But, first, you must take notice (I strike the keys in succession with my finger, from the one-lined _c_ to the highest treble) that these sounds grow higher and become sharper one after the other; and in this way (I strike the keys from one-lined _c_ to the lowest bass) you hear that the sounds grow lower and heavier.

The upper half, to the right, is called the treble; the lower half is the bass.

You quite understand now the difference between the high sharp tones and the low deep ones?
Now we will go on.

What you see here, and will learn to play upon, is called the key-board, consisting of white keys and black ones.

You shall presently learn to give the right names both to the white keys and the black; you see there are always two black keys and then three black keys together, all the way up and down the key-board.