Degrees of affinity of keys: in music everything is, as in mathematics!
The subject of classical harmony necessitates a deep examination of the interconnections between different keys. This relationship, first of all, is carried out by the similarity of several keys with common sounds (including key characters) and is called the relatedness of keys. First you need to clearly understand that, in principle, a universal system that determines the degree of relatedness of tonalities does not exist, since each composer perceives and implements this relationship in his own way. However, nevertheless, in musical theory and practice some systems exist and are firmly established, for example, Rimsky-Korsakov, Methodin, Hindemith and few other musicians.
The degrees of relatedness of keys are determined by the proximity of these keys to each other. The criteria for proximity are the presence of common sounds and consonances (mainly triads). Everything is simple! The more in common, the closer the connection! Explanation! Just in case – in the Dubovsky textbook (that is, the brigade textbook of harmony) a clear position is given regarding kinship. In particular, it was rightly noted that key characters are not the main sign of kinship, and, moreover, it is purely nominal, external. But what really matters is the triads on the steps!
DEGREES OF KIND OF TONALITIES ACCORDING TO THE ROMAN-KORSAKOV
The most widespread (by the number of adherents) system of kinship between the keys is the Rimsky-Korsakov system. It distinguishes three degrees or levels of kinship.
FIRST KIND OF DEVELOPMENT
This includes 6 keys, which for the most part differ by one key sign. These are the tonal systems whose tonic triads are built on the steps of the scale of the original tonality. These are: parallel tonality (all sounds are the same); 2 keys – dominant and parallel to it (one sound difference); 2 more keys – a subdominant and parallel to it (also a difference by one key sign); and the last, sixth, tonality – here are exceptions that need to be remembered (in major it is the tonality of the subdominant, but taken in the minor harmonic version, and in the minor – the tonality of the dominant, also taken into account the alteration of the 7th stage in the harmonic minor, and therefore major )
SECOND KIND OF KIND
There are 12 keys in this group (of which 8 are one mode mood with the original key, and 4 is the opposite). Where does the series of these keys come from? Here everything is like in network marketing: to the found keys of the first degree of kinship, partners are sought – your own set of keys … of the first degree! That is kindred to kindred! By golly, everything, as in mathematics – there were six, six more to each of them, and 6×6 only 36 – some sort of transcendence! In short, out of all found keys, only 12 new ones are selected (appear for the first time). They then will form a circle of the second degree of kinship.
THE THIRD DEGREE OF KIND
As you probably guessed, the keys of the 3rd degree of kinship are the keys of the first degree of kinship to the keys of the 2nd degree of kinship. Siblings to siblings. Here it is! An increase in the degree of kinship occurs according to the same algorithm. This is the weakest level of connection of keys – they are very far from each other. This includes five keys, which, when compared with the source, do not reveal a single common triad.
SYSTEM OF FOUR DEGREES OF KIND OF TONALITIES
In the brigade textbook (Moscow school – they inherit the traditions of Tchaikovsky) not three, but as many as four degrees of relatedness of keys are proposed. There is no significant difference between the Moscow and St. Petersburg systems. It consists only in the fact that in the case of a system of four degrees, the second degrees are divided into two. Finally … But why do you need to understand these degrees? And without them it seems to live well! The degrees of relatedness of keys, or rather their knowledge, will be useful when playing modulations. For example, on how to play modulations in the first degree from major, read here.