The Sanskrit verb krit means praising. In the Srimad Bhagavatam (10:21:5), there is a beautiful description of the Lords entrance to Vrindavan:
Bahrapeedam natavaravapuh karnayoh karnikaram
Bibhradvasah kanakakapisam vaijayanteem cha maalam
Randhran venoradharasudhaya karnayo karnikaram
Vrindaranyam swapadaramanam pravisad-gitakirtih.
Exhibiting an exquisite form resembling that of an actor, adorned with a crest of peacock feathers, wearing karnikara flowers on his ears, a wreath of flowers of five different colours and a golden cloth, and filling the holes of his flute with the nectar of his lips, the Lord entered Vrindavan, charming with his footprints, his glory being sung by hosts of cowherd boys.
The last word kirti denotes praise and from this is derived kirtan, which is now commonly known as a certain method of melodious singing. Only praising the name of the Lord and his lila, play, in melody for the purpose of keeping the flame of bhakti burning in the heart can be termed kirtan.
In this age, Vedanta and kundalini yoga are mere talk. They are not practicable for ordinary aspirants. Vedanta demands gigantic will, deep enquiry and wonderful powers of understanding and analysis. Very few possess these faculties. For kundalini yoga one needs great spiritual vigour and absolute brahmacharya for awakening the kundalini and taking it through the chakras to sahasrara. This is in theory; the practice is rather difficult.
So, in this kali yuga, sankirtan and practice of the formula, Be good, do good, alone will give God-realization. This alone can be practised by the vast majority of persons. Even those who practise Vedanta have all come down to the practice of sankirtan and nama smaran, always remembering the name.
You can study kundalini yoga and imagine that kundalini is passing from mooladhara chakra. It is some wind of acid passing through. Do not mistake it for kundalini shakti. Do kirtan. The kundalini will awaken by itself. Though Vedanta is good for lectures, for a spiritual person, the name is very pleasing. One who does kirtan need not deliver lectures on nava vidha bhakti, nine modes of devotion. All forms of bhakti are in the singing of kirtan. The veil of ignorance will be torn asunder by singing kirtan.
People do sankirtan with surprising enthusiasm and vigour for a year or two but after that they become slothful and torpid. The same zeal should be kept up throughout life. Just as food and drink are not dispensed with, even for one day, so also sankirtan should not be stopped even for a day. Sankirtan is indeed spiritual food. Nay, it is a physical and mental tonic as well. You can live on sankirtan.
While singing kirtan, the devotee is thrilled with divine emotion. He loses himself in the love for God. He weeps thinking of the glory of God. His voice becomes choked and he flies into a state of divine bhava. The devotee is ever merged in the Lords name and describing his glories to one and all. Wherever he goes, he begins to sing and praise the name. He requests all to join his kirtans. He sings and dances in ecstasy and he makes others dance also. However, such practices should be the outcome of a pure heart; they should not be merely a show. God knows the inner secrets of all. None can cheat the indweller. There should be perfect straightforwardness on the part of the devotee.
If all practise kirtan daily, the whole atmosphere will be purified. There will be abundant rain and abundant crops. In olden days there was kirtan in every house, and so there were good rains and good food. Therefore, if you really want peace and plenty, do kirtan.
The mind is purified by constant kirtan. It is filled with good and pure thoughts. Daily kirtan strengthens good samskaras. The mind of a person who trains himself in thinking good, pure thoughts, develops a tendency to think good thoughts. His character is moulded and transformed by continuous good thoughts. The mind that is ever intent upon singing the Lords names and glories has no occasion to take interest in the things of the world. Day and night the devotee feels the presence of God. This thins out the ego and one becomes sattwic and pure at heart. In fact, he who entertains thoughts of divinity actually becomes transformed into divinity himself. His bhava is purified and divinized. The meditator and the meditated, the worshipper and the worshipped, the thinker and the thought become one. This is samadhi. This is the fruit of kirtan.
May you live in the ocean of divine ecstasy in a fully illumined state, by the regular practice of sankirtan and complete self-surrender to the Lord.