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There is a big difference between a musical performance and kirtan. A performance is to display how good you are at something. In kirtan you don't have to prove anything, you have to get connected. That is the puropose of kirtan; to get connected yourself, and to help others get connected as well.
In a musical performance the main focus is on the notes and rhythm. In kirtan the focus is on the Shabad. The Shabad is transmitted through the kirtan. Music is the presenting tool. It is the plate that you use to serve up the Shabad.
The proper way to do kirtan is to please the Guru, don't please the audience. If you please the Guru and the audience is connected to the Guru then they will be pleased. If you are trying to please the audience, you might cross the line where your Guru will get unhappy with you.
Kirtan is the original form of Bani. Bani was first sung and written later on.