Madhusudana: One time I had the opportunity to chant while Prabhupada was present in a kirtan. Sometimes he would have devotees chanting kirtan rather than him doing it in the early days. I was always trying to be humble in whatever way I thought was humble. I was chanting not very loudly in order not to put myself forward as some great kirtan leader. Prabhupada shouted at me, “Chant loudly”. Over the years Prabhupada would say very clearly that boldly preaching was an act of humility, because it was the positive portion of humility. So if you preached loudly, then that took care of humility.
Reference: Remembrances by Sidhanta Das- Folio Vedabase
