Kirtan leaders should chant in the manner of the acharya… all should be pure devotees.
Regarding Kirtana Party: My idea is that at least one dozen persons should form a Kirtana Party. Two persons play mrdangas, eight persons play karatalas, one person playing tamboura, and one person playing melodious harmonium. The person who will play on tamboura will be leader singer. You have just calculated what I want, when you suggest that the leader should sing as I do, and the others will respond. That will be very nice. But all the members of the party will be pure devotees. None of them should be outsiders. We do not want any outsiders as far as possible. Mrdanga playing as you are doing at present will make you more and more expert as you go on playing. Here also I see Gaurasundara simply by playing is improving. If all the members keep their faith in Krishna and tries to please Him, certainly everyone will be pleased by hearing our Kirtana. It is sure and certain. When such Kirtana will be demonstrated, only the harmonium player may sit, and all the others may stand up and join the Kirtana and dancing properly dressed.
(Srila Prabhupada's letter to Hamsaduta, 4 February, 1968)