SIKHISM : What is meaning of 31 raags in Sri Guru Granth Sahib ?

Why bani is divided into ragas .
How it affects kitten ?
And why Jap Ji Sahib does not belongs to any raga ?
thank you

Nirvana

Our system of music is based on rage and Talia. According to Sikh courier, "the raga divides the octave in hundreds of different ways, each suited to the expression of particular mood, whereas the Talia reconciles the varying pulses of a thousand different lines through a complex structure of rhythm."

Before the birth of Guru Nanak, other saints of the Bhakti movement had also composed songs in various ragas and rhythms, which were sung to the accompaniment of musical instruments in the form of a kitten. But Guru Nanak used several kinds of verses, different types of poetry, and a number of ragas, regains and Grass and originated many more met res. He rendered for the first time mystic poetry in the style of classical music and Chase such ragas as would give tranquillity to the mind and sublimate the unusual nature of man through greater rythem.

In his compositions, Guru Nanak used 19 ragas out of which ten are morning ragas, four mid-day ragas and three evening ragas. The other two ragas are seasonal. The successors of Guru Nanak used traditional ragas. However, they introduced some changes to provde different melodies and to reflact intensity of divine aspiration. In the ragmala are mentioned 6 major ragas and 30 raginis (wives) and 48 sons, making a total of 84. In the Adi Granth, 31 ragas are used.

According to Guru Nanak Dev ji,

"It is not the raga nad
If the thought of one God is not in one's mind,
with mind attuned, dance, keeping the
steps in tune with the Infinite
with the fear of the Lord in mind, is the
real tuing of the dance;
And such a fear should always be in one's mind
everyday sitting and rising."

- Rag Asa

Kirtan should be sung day and night. Only the time spent in kirtan is fruitful. A discipline should pray to God for strength and courage and sing Hs praises.

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Bani( Guru's word) hymns are composed and complied in Guru Granth Sahib based on Indian classic Ragas as these hymns are meant to be sung in accompaniment with a musical instrument (harmonium or Verna) and Indian tabla (pair of drums), in a congregation. The singing is called Hari Kirtan. Rag is the most soothing measure to collectively sing or hear in silence when the word of God is sung, it torches ones inner most self.
Japji is the morning prayer of Sikhs which is to be read by an individual early in the morning, he can do so by heart or loud in ones own tune as he may like but Japji is not sung. Japji is the key statement of Sikh thought on divinity, spirituality, the world, the nature, our relation to God and religious philosophy, in short 38 or so stanzas.It is to meditated upon slowly and understood and hence not sung.