MUSIC. 



THE subject of Music will occupy two numbers 

 of the Information. The present number 

 will be to a certain extent introductory and tech- 

 nical, and will include the following subjects : 

 The Relation of Sound to Music ; Musical 

 Notation ; Scales, Keys, Intervals, and Chords ; 

 Theories of Harmony ; and the nature and capa- 

 cities of Musical Instruments. No attempt will 

 be made to teach executive music singing or 

 playing which cannot be learned from books ; 

 but the underlying principles will be sketched 

 as fully as our space will allow. The second 

 number will consist of a sketch of the history 

 of the development of musical art up to the 

 present time. 



SOUND AND MUSIC 



Before proceeding to give any account of the 

 methods adopted for representing musical sounds 

 upon paper, we must examine briefly the nature of 

 these sounds the physical basis upon which the 

 art of music rests. This matter properly belongs 

 to, and forms a part of, the science of acoustics, 

 but it is also so intimately connected with music 

 that it would be impossible for us to omit all 

 account of it here. We must assume at the 

 outset that our readers are acquainted with the 

 general fact that the cause to us of the sensation 

 which we call sound is the motion of the air or 

 other medium through which that sound is con- 

 veyed ; that if, for instance, a bell be struck in 

 a vessel from which air is exhausted, and in which, 

 therefore, there does not exist any medium by 

 which motion can be conveyed, no sound what- 

 ever is audible. When the motions of the air 

 which translate themselves into sound by our ears 

 are irregular, our sensation is that of a non- 

 musical sound ; but when they are regular, or 

 periodic, our sensation is that of a musical sound, 

 and it is with this class of sounds only that we 

 have to do here. 



The first thing to be examined into is the 

 nature of the 'regular motions' of the air just 

 referred to. These can be best explained by the 

 analogy which they present in every point to the 

 waves of liquid bodies. Every one is familiar with 

 the appearance of sea- waves, the long lines of 

 alternate ridges and furrows steadily moving for- 

 ward in a direction at right angles to their length. 

 On examination of these, the first point noticed 

 is the difference between the actual and apparent 

 motion of the water. A piece of wood floating on 

 the water is not carried forward by the waves, 

 but simply moves up and down in a vertical line, 

 according as the ridge or furrow of the wave 

 passes it ; its highest position being the level of 

 the former, and its lowest that of the latter. If 

 not influenced by wind, or tide, or current, it will 

 remain for ever over exactly the same spot. 

 Each particle of the water, when in a state of 

 wave-motion, will move exactly as the piece of 

 wood we have supposed ; it will oscillate between 

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two positions, and so be alternately higher and 

 lower than its neighbouring particles (which are 

 differently situated upon the wave, but which 

 oscillate themselves between precisely the same 

 limits), but it never moves forward in the direction 

 of the wave. The motion of the particles is, there- 

 fore, relative to each other only ; and if the waves 

 were to cease, and the water become calm, they 

 would occupy again precisely the same positions 

 that they occupied before the waves had risen. 



So much being understood as to the nature of 

 the real motion of each particle of water in a 

 wave, we may now look at the wave as a whole ; 

 and doing so, we find that it is conditioned by 

 three elements, knowing which for any particular 

 wave, we know all about it Of these elements, 

 the first and most important is its length by 

 which is meant the distance from crest to crest, 

 or from trough to trough of the wave. It is 

 obvious that the time in which a wave traverses 

 its own length determines, and is the same as, that 

 in which each drop makes one complete vibration 

 up and down. From this also we see that, for 

 waves travelling with equal velocities, the rate 

 of drop-vibration is inversely proportional to the 

 corresponding wave-length. Thus, if each of the 

 waves in one series is half the length of each of 

 the waves in another, but both are travelling with 

 the same velocity, it will be seen at once that 

 twice as many crests and troughs must pass any 

 point within any given time in the first case, as 

 in the second, and each drop will therefore have 

 made twice as many vibrations. Similarly, for 

 waves a third or a fourth as long, the drops will 

 vibrate three or four times as quickly. 



The amplitude of a wave is the vertical distance 

 between the top of its crest and the bottom of its 

 trough ; it is, therefore, exactly equal to the dis- 

 tance through which each drop moves, or to the 

 extent of its vibration. 



The/arm of a wave may vary as much as its 

 length or its amplitude ; it may be steepest on the 

 front or on the back, may have a sharp crest or 

 a rounded one, and so on through endless inter- 

 mediate forms. We have seen how the length of 

 a wave corresponds to the rate of the vibration of 

 its drops, and its amplitude to the extent of their 

 vibration ; in an exactly similar way, the form of 

 the wave determines their mode of vibration. If 

 a wave is steepest on its front side, the drop will 

 move upwards more quickly than it moves down ; 

 if the wave have a sharp crest and flat trough, 

 the drop will move more quickly (in both direc- 

 tions) in the upper half of its vibration than in the 

 lower ; and similarly, every different form taken 

 by the wave has a mode of drop-vibration with 

 which alone it can co-exist 



We may now define the motion of a wave as 

 being the 'uniformly progressive motion arising 

 out of a number of oscillatory movements," and 

 this definition enables us to take a larger view 



Sedley Taylor, Snatd m*d Music, p. & 



