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THE USEFULNESS OF THE FIFTH IN MUSIC. 
By the Bey, 0 . HOPE ROBERTSON, M.A. 
I. 
I N amateur musical work, either for home use or for train- 
ing a choir, difficulties are often found about the different 
keys in music, their signatures, and rules for transposing pieces 
up or down, as may he needed for suiting various voices. 
Now some most useful helps may he got on these points 
hy an examination of the musical interval of the fifth, from 
which hy a little cross-questioning we may draw some rules 
for popular use which are not generally found in musical trea- 
tises. These, in general, give directions without explanations 
of their modus operandi. 
We therefore propose to make the interval of the fifth in 
music perform a little “ musical magic,” and tell us these 
points : — 
1. In what order different keys follow each other. 
2. What notes are to he made sharp or flat in the signa- 
tures, and in what order they follow each other. 
3. How to know by inspection what keys pieces are written 
in, and into what they may be transposed. 
4. What changes have to he made in the signatures of keys 
to transpose pieces up or down, any number of notes. 
II. We must first, for the sake of clearness, recall to mind 
a few definitions of musical terms necessary for our purpose. 
The ear teaches us that a certain sequence of notes rising up 
from the starting note or key note, such as C, must follow each 
other in a certain regular course, if a pleasant effect is to be 
made, and this succession of notes is called the major scale of 
that note. It comprises eight notes, the last being the octave 
above the key note. It is found on examination that the 
interval between these notes are as follows : — First, 2 whole 
tones, then 1 semitone ; next, 3 more whole tones and 1 more 
semitone : or to put it in a series of letters, marking the semi- 
