MUSIC blend into smooth continuous sensations, but produce beats, corresponding in number to the rate of vibration indicated above. These grave sounds cannot be used alone, but are always sounded in unison with pipes or instruments giving their higher octaves and harmonics. Thus the latter are compounded with the harsh fundamental of the grave note, and at the same time blend with any harmonics which may accompany the fundamental of these grave sounds. In the higher regions of musical sounds, pianos give the notes A and even 0, of 3,520 and 4,224 vibrations. The most acute sound of orchestral music is the D (of 4,752 vibrations) of the piccolo flute. There are three distinctions to be made among- sounds : their pitch, of which we have just spoken; their intensities, concerning which it is not necessary to enlarge ; and their timbre, or that character by which we distinguish between sounds having the same pitch and intensity. All simple sounds, which we define as those having only one pitch, have the same timbre. Such aro the sounds given by flue organ pipes, or by tuning forks when mounted on resonant boxes. But the sounds employed in music are always composite, being formed of several sim- ple sounds whose numbers of vibrations are to each other generally as 1, 2, 3, 4, &c. ^ Sim- ple sounds are unfit for musical expression by reason of their want of brilliancy ; for this rea- son the notes of closed flue pipes are rarely sounded alone, but to invest their tones with feeling and life they are combined with other stops, giving the harmonics or furniture of their simple sounds. The sounds of the flute approach in character those given by closed organ pipes; but when associated with other instruments which bring out the sequence of the harmony, the flute, by reason of the per- fect softness of its sounds and the facility with which it renders rapid movements, is charm- ing, and cannot be replaced by any other in- strument. It held a far more important place in ancient than in modern music; but even among the ancients the abler masters preferred the more thrilling sounds of stringed instru- ments. The sounds of all other instruments, as well as the notes of the human voice, are composite, formed by the blending of several simple sounds, having different positions in the musical scale. (See HARMONY.) Helm- holtz has proved that the distinctive timbre of any given sound is due to the number and rel- ative intensities of its elementary sounds, or harmonics. Stopped wooden flue pipes of large section give nearly simple sounds when blown with a feeble pressure. An increase of pres- sure in the blast develops the third harmonic, and an excessive pressure may injure the tim- bre of the sound by giving to it too great an intensity compared with that of the funda- mental ; it may even cause the latter to dis- appear, and then the whole sound will have risen in pitch by an octave and a fifth. Stop- ped organ pipes having small area of section compared with their lengths give the fifth harmonic as well as the first and third. In other words, closed pipes give the uneven har- monics ; open and narrow pipes give the com- plete series of harmonics up to a certain num- ber. Thus, if we close all the holes in a flute and blow gently, and then with increasing in- tensity, the instrument will successively give the first, second, third, and fourth harmonics. In the case of the narrow open pipes in the organ (viola, principal, violoncello, contra-bass, viola-di-gamba), powerful pressure of wind gives the fundamental sounds of these pipes accompanied by the clear sounds of all the harmonics, including the sixth. It is quite otherwise in the case of the large open pipes. From the considerable mass of air which they contain, and from the fact that they do not readily jump in their pitch from the funda- mental to one of the harmonics on increasing the wind pressure, these large pipes form the basis of the mass of sounds of the organ, and hence they have been called the principal re- gister. In these pipes the fundamental sound is intense, and is accompanied by a few har- monics of feeble intensities. In the flute or chimney pipes, the timbre receives a brilliant character from a small open pipe adapted to the top of these closed pipes. By combining the stops on the organ, one can produce a great vari- ety of timbre ; and in this regard the organ has the advantage over all other musical instru- ments. Vibrating plates, or reeds, are used in the reed pipes of the organ, in the melodeon, and in the clarinet, hautboy, and bassoon ; while in the horn, trumpet, trombone, and cornet the lips perform the office of the reed. The sounds of all reed instruments are peculiarly rich in harmonics; it is not difficult to distinguish those even as high as the twentieth. The fun- damental, or some powerful harmonic, is gen- erally reenforced in reed organ pipes by sur- mounting them with open or partly closed tubes of various sizes and forms ; and thus are obtained the various timbres of these instru- ments, such as the trumpet, vox liumana, &c. The clarinet gives only the odd series of har- monics, 1, 3, 5, 7, &c., while the hautboy and bassoon give the entire series, 1, 2, 3, 4, &c. If the hautboy takes one note of an interval and the clarinet another, some concords will sound best when the former instrument, others when the latter takes the upper note. Among stringed instruments those of the violin kind occupy the highest place. The tones of these are highly complex, containing the clear sounds of the higher harmonics from the sixth to the tenth ; and as violins do not, like the piano, give fixed sounds evolved by a keyboard, they have great sonorous flexibility, giving the per- former the power of playing in any mode or scale, and of gliding from one note to another without perceptibly breaking the continuity oJ the sound ; and above all, he can obtain any note with varying intensity, and thus express his feelings by the most exquisite modulation.
