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Scan 23
A dictionary of musical terms, 1889
24 lines. Read by computer on 9 September 2026. No printed page number was found. See the scan on archive.org.
1ACOUSTICS—ACT.
3The above explanation of the cause of dissonance is also due to Helmholtz, and completely solves a question which had remained unanswered since the time of Pythagoras, although that philosopher made the important discovery that the simpler the ratio of the two parts into which a vibrating string was divided, the more perfect was the consonance of the two sounds.
521. The sound of the piano, violin, &c., is only in a small measure due to the actual vibration of the strings themselves. The latter communicate their own motion to the sound board of the piano, and to the front, back, and enclosed air of the violin. In the latter instrument communication is made to the surrounding air from that within it by means of the f holes.
7If a string were merely stretched between two pegs firmly fixed in a stone wall and caused to vibrate, scarcely any sound would be heard at all, owing to the mass and rigidity of the wall, which would refuse to be thrown into vibration by so small an amount of energy as that which the string would possess. On the other hand, the sound board of a piano readily answers to the vibrations imposed on it when the string is struck, and having a large surface in contact with the air, every point of which originates a system of waves, it causes a full and powerful sound.
922. The vibrations of straight rods may be either longitudinal or transversal. The former have not been generally employed for the production of musical sounds; the latter are such as take place when a tuning fork is struck, or when a musical box or triangle is played. In the case of a curved rod the vibrations are more complicated, but there is one interesting case, namely, that in which the curved rod takes the form of a circular ring. In this case the fundamental tone is obtained by suspending it horizontally by four strings attached at equidistant points in the circumference, and by lightly tapping it midway between any two. If the number of vibrations then given be 2n per second, those of the successive harmonics are proportional to 3n√6, 4n√13, 5n√22, &c.
1123. The nature of the vibrations of a bell may be partly inferred from those of a ring, as the bell may be considered as consisting of a connected series of rings of different diameters all vibrating simultaneously; thus the fundamental tone of a bell would cause it to divide itself longitudinally into four equal segments, corresponding to the four quadrants into which the suspended ring divides. The period of its vibrations could not, however, be similarly inferred.
1324. The vibration of plates is not, musically speaking, a subject of much interest, as the only instruments which depend upon it directly for the production of their sounds, are gongs and cymbals, and the same may be said of membranes. Chladni was the first to show the positions of the lines of nodes on a plate, by clamping it horizontally in a vice, and causing it to vibrate by passing a violin bow over one edge, having previously sprinkled it with a little sand. The lines of nodes being those parts of the plate which, like the nodes of a string (§ 13), are not thrown into vibration, remain covered with the sand which collects there from the vibrating portions, and in this way very curious and interesting figures are produced.
15Act (Acte, Fr.; Akt, Ger.; Atto, It.) A distinct division in the plot or design of a drama or opera, forming an incident complete in itself, but bearing reference to the general idea of the whole. Every dramatic plot naturally divides itself into three portions: the exposition, the development, and the conclusion; and this division would seem to point to the separation of a dramatic design into three acts, but where the piece is in four, five, or more acts, it will be found on examination that the tripartite division is essentially the same, greater prominence or care in detail being given to one or more of the sections. Thus the exposition may be spread over two or three acts, the development over one or two, and the conclusion or unravelling, reserved for the final act.
17The classical trilogies—groups of three tragedies—were most frequently united by a common idea, each forming a complete incident, connected by a bond of sympathy, sentiment, or subject with the grand design.
19Bartholomé Torres Naharro, of Torre in Spain, who wrote at the commencement of the 16th century, is said to have been the first who suggested the division of plots into acts, or jornados, although Cervantes claims the invention for himself. It is certain that Naharro's printed dramas are not so divided.
21Donaldson, in speaking of the Æschylean Trilogy (the Agamemnon, Choephorœ, and the Eumenides), says, that the three plays mutually cohere, is plain; and as they were actually brought on the stage in sequence, they may be regarded as so many acts of one grand heroic drama. This is mentioned, in order to vindicate the practice of Shakspeare and other modern dramatists, in compressing into one drama an extensive cycle of human destinies; because the very objection that has been made to the practice is the alleged example of the ancients to the contrary.
23Wagner's Nibelungen trilogy, though stated to be "new from end to end" in idea and design, bears a close affinity to the ancient Greek drama. For the subject is mythical
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