Playable BooksPyotr Ilyich Tchaikovsky · section 3 of 36
Chapter I. The Triads of the Major Scale
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§ 4. If we construct a triad on each successive degree of the diatonic major scale, we obtain the following chords:
On the 1-st, 4th and 5-th degree we find major triads:
These triads, representing the most essential constituents of the major scale, bear the names of those degrees of the scale, on which they are based.
The triad on the 1-st degree is termed the Tonic triad ” » » » 4th,. > » Subdominant triad » » » » oth, ” » » Dominant triad
§ 5. It has just been said that these three major triads form the most essential constituents of the major scale. Verily they contain all the diatonic degrees of the scale; and, being most closely related to one another, they indicate clearly and unmistakeably the key and further suffice for the harmonic accompaniment of any melody that does not surpass the limits of the key in question. Their mutual affinity is easily demonstrated by the degree of relation existing between the several scales to which they belong. The triads on the 4-th and 5-th degrees, while they are respectively the Subdominant and Dominant in the harmony of the given key, are at the same time the tonic triads of those keys, which, in the so-called,,Circle of Fifths* are nearest to the given key. So that the inner relationship of the three major triads in the harmony of the major scale is in direct proportion to the degree of relationship of the three successive keys in the Circle of Fifths (their Tetrachords being common)
§ 6. In the major scale minor triads are also found, namely on the 2-nd, 3-rd and 6-th degrees. The minor Third imparts to these triads a soft, weakened character, hence they cannot command the importance possessed by the major triads. However, they furnish us with a beautiful contrast to the latter, emphasizing their strength! Their mutual affinity is the same as that of the major triads, as they possess the same proximity in the Circle of Fifths.
Of the degree of their relationship to the major triads we may say it is the same as that existing between parallel keys; for the chords on the l-st and 6-th degrees, the 5-th and 3-rd degree and the 4-th and 2-nd degree respectively are separated by a minor third.
The whole mass of major and minor triads may be grouped into three sets of two triads each:
a) The tonic group viz: the triads on the 1-st and 6-th degrees.
b) The dominant group viz: the triads on the 5-th and 3-rd degrees and c) The subdominant group viz: the triads on the 4-th and 2-nd degrees.
§ 7. In marked contrast to the other triads stands the diminished triad on the 7-th degree, because of its dissonant character. We shall return to this chord later on, having first entirely mastered the connection of the other six triads.