Guru Nanak Sahib used to call a group of people singing bhajans as Bhajan mandali, as we now call those meetings Satsang. When we are all sitting together, everybody knows that we are coming together in the remembrance of God. Everyone who is in that group has the thought of God at that time. That's why Guru Nanak Sahib says, "Whenever you sit together in Satsang, first of all, all of you should sing some song or bhajan which is full of yearning and love for the Master and Satsang."
We are not to sing the bhajans as a ceremony or rite or ritual. We should sing the bhajans with yearning. Guru Nanak says, "Whenever you sing bhajans, if you sing with love and yearning within you, that singing will give you such intoxication and peace that lust, anger, greed, attachment, egoism, all these fires which are burning within us, will begin to cool." That intoxication which we get from singing the bhajans with yearning and love removes our suffering.
The bhajans which we sing here have come out from the mouths of great Masters, and they show Their yearning. When we sing those bhajans, we should also try to develop that yearning.