Scan 35
The American history and encyclopedia of music .., 1908
22 lines. Read by computer on 11 September 2026. Printed page 13. See the scan on archive.org.
1acoustics
2side it will not only return to its original position, but will spring as far in the opposite direction as it was pulled from the first position. This double motion is a vibration and will continue until the force of movement is spent. It is the vibration of the individual particles composing it which causes the string to vibrate, and therefore vibration may be defined as the moving backward and forward of the particles composing an elastic body. The distance between the extreme points reached by a particle is called the amplitude of vibration, and upon this factor depends the degree of loudness of a sound. The tighter a string is stretched the greater will be the number of its vibrations per second and the higher the pitch of the resulting tone. The shorter, finer and lighter a string is also increases the vibrations and consequent height of tone. The lowest musical tone, proper, contains forty-one and one-fourth vibrations per second. Higher tones have a more forceful effect upon the ear than lower ones and can be heard at a greater distance.
4The reason that the same tone when struck on different instruments has different qualities is because of the accompanying vibrations, or partial tones, produced by the instrument upon which the tone is struck. The mere vibration of a piano or violin string produces very little sound. This must be strengthened by some such means as the sounding-board in the piano, or the sounding-post in the violin, which conveys the vibrations from the strings to the back of the instrument.
6The air, vibrating with sound waves, strikes upon the delicate tympanic membrane of the ear, causing it to vibrate and thus to irritate the auditory nerves which analyze every sound entering the ear into its component parts; and in this way are conveyed to the brain the various characters of the complex sounds about us.
8In the vibration of a column of air in a pipe, the use of the pipe itself is to imprison the air and by its length and bore modify the sound. The longer the pipe the lower the sound. The column of air is made to vibrate by the motion of some vibrating object placed at the open end of the tube.
10Sound waves travel by communicated motion. The different particles of which the air is composed do not change their positions materially, but simply pass on in turn a motion which has been conveyed to them by other particles. As air becomes warmer it is more elastic and will allow sound waves to travel faster. Sound travels faster in water than in air because water is more elastic.
12Although much study has been given to the acoustic properties of buildings architects are still confused on this subject, so slight are the causes which will produce sound effects. Even hangings or small irregularities will cause a great difference in the acoustics of a hall.
14act
15One of the main divisions of a drama or opera, which although complete in itself has its part in the development of the whole. Even in the early Greek plays the division was made by the appearance of the chorus, although no name was used. The Roman plays were divided into acts, five being the proper number according to Horace. There is no set number of acts into which a drama or opera must be divided, but as a rule the grande opéra is in five acts, the opéra comique and the opéra bouffa in three or one, while the Italian and German operas have different numbers, three being most common. The word, act, was also applied to the divisions of an oratorio, and the parts of a concert or musical entertainment. Equivalent to acte (Fr.), akt (Ger.), atto (It.).
17act-tune
18Instrumental music performed between the acts of a play. These act-tunes during the latter part of the Seventeenth and the early part of the Eighteenth Century were especially composed for the play which they accompanied, together with "first and second music" played previous to the overture. Later the works of the noted composers took the place of the special act-tunes and now usually the popular music of the day is played.
20acte de cadence (ăkt-dŭ-kă-dăñs) Fr.
21Act of making a close: applied to a movement or progression in one part, particularly in the bass, which forces the other parts to join in making a close, or in avoiding one at the end of a passage. The two chords which introduce the final accent.
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