AbhishekSarki , look at the construction of the melody, its shape, rhythm and harmony. The melody is divided into 4 sections of eight bars - AABA
. The melody begins and ends with C, which, like a magnet, attracts the rest notes of section A
. So this pitch does not contain tension ; and in bar 8 actually release some tension in previous bar. Hence, a chord based on C , which is called Â In this section tonic
, , will also be the most calm . This means that the other chords will be less calm, especially the dominant at fifth step - G , and even more tense, if you add to it the seventh F. So, chord I is the most calm, chord V(7) is the most tense , chords IV and VI are between them.
If we consider only the melody, then it is necessary to take into account the parameter of melodic intonation - the ascending and descending melodic curve. Its natural basis is speech-melody, reflecting the emotional subtext : the more contains tension , the higher melodic line rises up , and often also dynamics. With the exception of the first measure, all high pitches are supported by less stable chords.
However, this is not all; there is relationship of melodic pitches and chords. The acoustic hierarchy of pitches in chords is associated with a system of overtones, where higher overtones create more tension. Thus, in the major and minor triads, the order of tension of each step in ascending order: I ,V,III ; and VI and VII are next.
And this, too, is not all; there is a factor of rhythmic acceleration, associated with excitation - as in bars 2,6, and 7 .
If we weigh all the parameters, then the most tense measures in part A are 2,5, 7; and the most tense point in whole song -bar 22(because of new and only , most unstable chord D ) . This point is called the golden section, and here is culmination of the song.