There are, however, simpler pieces of counterpoint than a fugue. Sometimes, as in the charming little "Gavotte" by Padre Martini, which now and then figures among the lighter numbers on the programs of historical recitals, the contrapuntist combines a theme with itself, or, rather, "imitates" it, which is a simple form of the canon. Another form of canon is the round of which "Three Blind Mice" is a familiar example. How many people, when singing this, have realized that they were being initiated into that mysterious thing known as counterpoint? A comparatively simple form of counterpoint is well illustrated by a dapper little piece in Bach's "Two-Part Inventions," in which the spirited theme given out by the right hand answers itself a bar later in the left, an "imitation" which crops out again and again in the piece and gives it somewhat the character of a canon.
For any one who wishes to become acquainted with Bach there is nothing better than these "Two-Part Inventions," especially the fascinating little piece from which I have just quoted, compact, buoyant and gay, even "pert," as I once heard a young girl characterize it; a perfect example of old Father Bach in moments of relaxation when he has laid aside his periwig and is amusing himself at his clavichord.
Bach's fugues, and especially his "Well-Tempered Clavichord," forty-eight preludes and fugues in all the keys, form the climax of contrapuntal music. Goethe once said that "the history of the world is a mighty fugue in which the voice of nation after nation becomes audible." This is a freely poetic definition of that highly complicated musical form, the fugue. Let me attempt to illustrate it in a different way.
Imagine that a composer who is an adept in counterpoint places four pianists at different pianofortes, and that he gives a different theme to each of them, or a theme to one and modified versions of it to the others. He starts the first pianist, after a few bars nods to the second to join in with his theme, and so on successively with the other two. It might be supposed that when the second player joins in, the two themes sounding together would make discord, which would be aggravated by the addition of the third and fourth. But, instead, they have been so conceived by the contrapuntist that they sound well together as they chase and answer each other, or run counter to and parallel and enter into many different combinations, sometimes flowing along smoothly, at other times surging and striving, yet always, in the case of a truly great fugue, borne along by a momentum as inexorable as the march of Fate. Of course, it must not be supposed, because I have called four pianists into action in order to emphasize how distinct are these themes, which yet, when united, are found to blend together, that several players are required for the performance of a complicated piece of counterpoint like a fugue. What is demanded of the player is entire independence of the fingers, so that he can clearly differentiate between the themes and enable the hearer to distinguish them apart, even in their most complicated combinations. An edition of Bach's "Well-Tempered Clavichord" by Bernardus Boekelman prints the themes in different colors, so that they are easy to trace through all their interweaving, and is interesting to study from.