It is well known what a musical line is. Most musical instruments have a linear character. The pitch of the different instruments corresponds to the breadth of a line: violin, flute, and piccolo produce a very thin line, viola and clarinet a somewhat thicker one; and by way of the lower instruments, one arrives at broader and broader lines, right down to the lowest notes of double bass or tuba.

Apart from its breadth, various colors of line are produced by the manifold colors of different instruments.

The organ is just as much a typical line-instrument as the piano is a point-instrument.

It may be suggested that in music, line offers the greatest store of expressive resources. Here, line operates in exactly the same temporal and spatial way as is to be seen in painting. How time and space relate to one another in these two arts is another question. The differences between them have perhaps given rise to exaggerated disquiet, with the result that the concepts time-space and space-time have been so widely separated from one another.

The scale of values from pianissimo to fortissimo can be expressed by increasing or decreasing intensity of line, or by its degree of lightness. The pressure of the hand upon the bow corresponds perfectly to the pressure of the hand upon the pencil.

Wassily Kandinsky, Point and Line to Plane 1926, 617-18