Hardly any musician, especially an instrumentalist, likes to delve into the theory of music. Most prefer to concentrate on the typically practical aspects, i.e. concentrate on the instrument. However, knowing some of the rules can turn out to be very useful in practice. These include the knowledge of the kinship system between the individual scales, which is really about the ability to quickly decode the key and the ability to transpose, which is based on the so-called the principle of the fifth circle.
Each piece of music has a specific key, which consists of specific notes assigned to a major or minor scale. We can already determine the key of a given piece after looking at the notes for the first time. It is defined by key signs and chords or sounds that begin and end the work. The harmonic relations within the key between the main scale steps and the minor ones are also important. We should look at these two factors together and not be influenced only by the key signs or the opening chord itself. Each major scale has a related minor key with the same number of signs next to the clef, and for this reason the first and usually the last chord in the work, which constitutes the tonal chord, is such a supporting element as to the key.
Acord tonalny – Tonika
It is with this chord that we most often start and end a piece of music. The name of the scale and the key of the piece are derived from the name of the tonic note. The tonic chord is built on the first degree of the scale and belongs, next to the subdominant, which is on the fourth degree, and the dominant, which is on the fifth degree of a given scale, to the three most important chords constituting the harmonic triad, which at the same time constitutes the harmonic basis of the work.
Related tones – parallel
It is one of the basic elements of the major-minor system, which defines the relationship between particular major and minor keys, which have the same number of chromatic marks of crosses or flats next to the key. This is one of the reasons why, when deciphering the key in a piece, one should also look at the opening chord that begins a given piece of music, because not only the number of signs by the key determines the key, but also the tonal sound. On the other hand, the easiest way to find a related key with the same number of signs is to play a minor third down from the tonal note, that is, the tonic lying on the first step. In the key of C major, a minor third down from the note C will be the note A and we have a minor scale in A minor. Both of these ranges have no sign on the key. In G major a minor third down this is going to be E and we have a minor scale in E minor. Both of these ranges have one cross each. When we want to create a key related to a minor scale, we chronologically make a minor third upwards, e.g. in C minor and E flat major.
Related identical tones
These keys have a different number of signs on the keys and the common feature is a tonic sound, eg in A major and A minor.
The principle of the fifth circle
The purpose of the fifth wheel is to facilitate and organize the scales according to the incoming chromatic signs, and it is a relationship of order. We make the fifth up from the tonic and in each subsequent scale one additional chromatic mark is added. They start with the C major scale, which has no key signs, we make the fifth up from the tonic or note C and we have a G major scale with one cross, then a fifth up and we have D major with two crosses, etc. etc. For the scales For moles, our fifth circle changes its direction of motion to the opposite and turns into a square circle, because we move back down a fourth. And so, from the A minor scale and the sound and the fourth down, it will be the E minor scale with one character, then the B minor scale with two characters, etc. etc.
Knowing the fifth wheel makes it much easier to build the order of individual scales, and thus makes it easier for us to transpose pieces to the next key. It is also used in the practical learning of scales, arpeggios and chords. It is useful in finding functional relationships between chords in a certain key. In a short time you will realize that this theoretical knowledge significantly improves our work in practice. For example, it greatly facilitates improvising, because we know which sounds we can use and which should be avoided.