There are three modes of communication: in head to head communication you talk, in heart to heart communication you sing, and soul to soul communication happens in silence.
When you meet with people, often you communicate from head to head. When you are with nature, you start singing, you communicate with nature from your heart. Often when you are with people you keep talking, blabbering, and you keep the communication on the level of the head only. But when you are with nature, you start humming and your communication comes through the heart. And when you are with the guru, you go blank and forget all the questions. Then communication comes through the soul in silence.
When you meet with people, you like to remain in the head, you seldom sing with people (other than when it is organised). Your ego obstructs you from singing. Many do not feel comfortable singing with people. When you sing with people then you descend to the heart level or feeling level. Some feel comfortable just listening to music. Some feel comfortable singing only when they are alone. Some sing to draw attention or to charm others. Some only want to join in when all the others are singing. All this singing comes from ego.
Bhajan means sharing, sharing from the deepest level of our existence. Bhajan is authentic sharing. If you could sing with people, then your ego shatters. Children can sing with people for they do not have ego. To sing with a stranger you have to be free of ego. Ego doesn't let you sing with a stranger. Head level is safe for the ego -heart level breaks the ego - soul level dissolves the ego. All communication gaps happen because of ego.
Exercise: when you are with people, rather then chatting just start singing and you can feel the shift of energy that is happening. If you want to have more fun, greet a stranger with a song.