A Dictionary of Music and Musicians/Timbre

TIMBRE. A French word, originally signifying a bell, or other resonant metallic instrument, of which the sense was subsequently extended to denote peculiar ringing tones, and lastly employed by the older writers on Acoustics to indicate the difference between notes which, though of identical pitch, produce dissimilar effects upon the ear. The cause of this variety not being then understood, the vagueness which characterises the expression was hardly misplaced. But the researches of Helmholtz put an end to the ambiguity, by showing that difference of timbre was due to change in the upper-partial tones, or harmonics, which accompany the foundation-tone, or ground-tone, of a note or sound.

A somewhat better, but rather metaphorical phrase was afterwards suggested in Germany; by which varieties of timbre were termed Klangfärbe or Sound-colours. This term, in the outlandish shape of 'Clangtint,' was adopted by Tyndall and other writers as an English equivalent of the German word.

But a term has been latterly employed which must commend itself to all as at once a pure English word and a symbol to express the idea, now become definite; namely the word Quality. A sound may therefore be said in fair English to possess three properties, and no more—Pitch, Intensity, and Quality; respectively corresponding to the Frequency, the Amplitude, and the Form of the Sound-wave. In case this definition be objected to as unnecessarily geometrical, the Quality, or Timbre, of a note may be described as the sum of the associated vibrations which go to make up that complex mental perception.

'If the same note,' says Helmholtz,^[1] 'is sounded successively on a pianoforte, violin, clarinet, oboe, or trumpet, or by the human voice, notwithstanding its having the same force and pitch, the musical tone of each is different, and we recognise with ease which of these is being used. Varieties of tone-quality seem to be infinitely numerous even in instruments; but the human voice is still richer, and speech employs these very qualitative varieties of tone in order to distinguish different letters. The different vowels belong to the class of sustained tones which can be used in music; while the character of consonants mainly depends on brief and transient noises.'

It is well known that he analysed these compound tones by means of Resonators, and subsequently reproduced them synthetically by a system of electrically controlled tuning-forks. The full demonstration of these facts occupies the larger part of his classical work on 'Sensations of Tone,' and can hardly be given in a brief summary. Pure tones can be obtained from a tuning-fork held over a resonance tube, and by blowing a stream of air from a linear slit over the edge of a large bottle. The quality of tone in struck strings depends on (1) the nature of the stroke, (2) the place struck, and (3) the density, rigidity, and elasticity of the string. In bowed instruments no complete mechanical theory can be given; although Helmholtz's beautiful 'Vibration Microscope' furnishes some valuable indications. In violins, the various parts, such as the belly, back, and soundpost, all contribute to modify the quality; as also does the contained mass of air. By blowing across the f-hole of a Straduarius violin, Savart obtained the note c'; in a violoncello, F; and in a viola, a note one tone below that of the violin.

Open organ pipes, and conical double reed instruments, such as the oboe and bassoon, give all the notes of the harmonic series. Stopped pipes and the clarinet give only the partial tones of the uneven numbers. On this subject, neither Helmholtz nor any other observer has given more detailed information: indeed the distinguished German physicist points out that here there is still 'a wide field for research.'

The theory of vowel-quality, first enunciated by Wheatstone in a criticism on Willis's experiments, is still more complicated. Valuable as are Helmholtz's researches, they have been to some extent corrected and modified of late by R. Koenig in his 'Experiences d'Acoustique.'^[2] The latter writer begins by stating that, according to the researches of Donders and Helmholtz, the mouth, arranged to produce a particular vowel-sound, has a powerful resonance-tone which is fixed for each vowel, whatever be the fundamental note. A slight change of pronunciation modifies the sound sufficiently to sustain the proposition made by Helmholtz of defining by these accessory sounds the vowels which belong to different idioms and dialects. It is therefore very interesting to determine the exact pitch of these notes for the different vowels. Helmholtz and Donders however differ considerably in their results. Koenig determines the accessory resonance-tones for the vowels as pronounced by the North-Germans as follows:—

OU	O	A	E	I
B♭2⁠	B♭3⁠	B♭4⁠	B♭5⁠	B♭6
225	450	900	1800	3600	vibrations.

The simplicity of these relations is certainly in their favour, and is suggested by M. Koenig as the reason why we find essentially the same five vowels in all languages, in spite of the undoubted powers which the human voice possesses of producing an infinite number and variety of such sounds.

[ W. H. S. ]

1. 'Sensations of Tone,' Ellis's transl. p. 28.
2. Quelques Expériences d'Acoustique, Paris 1882 (privately printed). Essay vi. p. 42.