is the real Subject; but attention to the Exposition will generally decide the point. Should the Canto fermo pass through a regular Exposition, in the alternate aspects of Dux and Comes, it may be fairly considered as the true Subject, and the ostensible Subject must be accepted as the principal Counter-Subject. Should any other Theme than the Canto fermo pass through a more or less regular Exposition, that Theme is the true Subject, and the Canto fermo merely an adjunct. Examples of the first method are comparatively rare in Music later than the 17th century. Instances of the second will be found in Handel's 'Utrecht Te Deum and Jubilate,' 'Hallelujah Chorus,' 'The horse and his rider,' Funeral, and Foundling Anthems; and in J. S. Bach's 'Choral Vorspiele.'
Other exceptional forms are found in the 'Fugue of Imitation,' in which the Answer is neither an exact reproduction of the Subject, nor necessarily confined to Imitation in any particular Interval; the Fughetta, or Little Fugue, which terminates at the close of the Exposition; and the Fugato, or Pezzo Fugato, which is not really a Fugue, but only a piece written in the style of one. But these forms are not of sufficient importance to need a detailed description
[App. p.799 "From a passage in Arthur Bedford's 'Great Abuse of Musick' (1711) it may be inferred that the invention of tonal fugue was commonly ascribed, though of course wrongly, to Purcell. He gives an example in his appendix of a 'Canon of four parts in one, according to Mr. Purcell's rule of Fuging, viz. that where the Treble and Tenor leaps a fourth, there the Counter and Bass leaps a fifth.'"]
TONALITY is the element of key, which in modern music is of the very greatest importance. Upon the clearness of its definition the existence of instrumental music in harmonic forms of the Sonata order depends. It is defined by the consistent maintenance for appreciable periods of harmonies, or passages of melody, which are characteristic of individual keys. Unless the tonality is made intelligible, a work which has no words becomes obscure. Thus in the binary or duplex form of movement the earlier portion must have the tonality of the principal key well defined; in the portion which follows and supplies the contrast of a new and complementary key, the tonality of that key, whether dominant or mediant or other relative, must be equally clear. In the development portion of the movement various keys succeed each other more freely, but it is still important that each change shall be tonally comprehensible, and that chords belonging to distinct keys shall not be so recklessly mixed up together as to be undecipherable by any process of analysis—while in the latter portion of the movement the principal key again requires to be clearly insisted on, especially at the conclusion, in such a way as to give the clearest and most unmistakeable impression of the tonality; and this is commonly done at most important points by the use of the simplest and clearest successions of harmony. Chords which are derived from such roots as dominant, subdominant, and tonic, define the tonality most obviously and certainly; and popular dance-tunes, of all times, have been generally based upon successions of such harmonies. In works which are developed upon a larger scale a much greater variety of chords is used, and even chords belonging to closely related keys are commonly interlaced without producing obscurity, or weakening the structural outlines of the work; but if chords are closely mixed up together without system, whose roots are only referable to keys which are remote from one another, the result is to make the abstract form of the passage unintelligible. In dramatic music, or such music as depends for its coherence upon words, the laws which apply to pure instrumental music are frequently violated without ill effects, inasmuch as the form of art then depends upon different conditions, and the text may often successfully supply the solution for a passage which in pure instrumental music would be unintelligible.
TONE, in the sense of Quality, the French timbre, is distinguished as harsh, mild, thin, full, hollow, round, nasal, metallic or woody; and most persons agree in assigning these epithets to varieties of tone as usually heard. No valid reason was forthcoming for the cause of these varieties until Helmholtz, in 'Die Lehre der Tonempfindungen,' settled its physical basis, demonstrating and explaining it by his theory of tone sensations. Since the publication of that great work the why and wherefore of differences of quality may be learned by all enquirers, without any preliminary knowledge of mathematics; and as there are admirable translations of Helmholtz's great work, in French by M. Gudroult, and in English by Mr. A. J. Ellis, those who wish to pursue the study of the subject will find no insurmountable hindrance to doing so.
If, as Helmholtz points out, the same note is sounded successively on a pianoforte, a violin, clarinet, oboe or trumpet, or by the human voice, though the pitch be the same and the force equal, the musical tone of each is different and may be at once recognised without seeing the instrument or singer. These varieties of quality are infinitely numerous, and we can easily distinguish one voice from another in singing or speaking even by memory, at distances of time and space; and by the delicate shades of quality in vowel tone we perceive that each individual is furnished with a distinct vocal instrument. This infinite gradation of tone is due to the fact that simple tones are very rarely heard, but that in nearly every musical sound, though accepted by the ear as one note, several notes are really heard in combination, and it is the different relative numbers and intensities of the notes combined that cause the sensation of different quality. In the analysis of the combination the lowest tone is called the 'Prime' or 'Fundamental,' and the higher ones, the 'Upper Partials.'[1] The running off into upper partial tones is to be attributed, as Mr. Hermann Smith discovered, to the energy with which the sounding medium, whatever it may be, is agitated. The Æolian Harp is a beautiful instance of the influence of varying energy. In it several strings are tuned to one pitch, but they are not equally sub-
- ↑ We abstain from reference to the much-debated combination or differential tones which the ear can perceive lower in pitch than the fundamental.
