There is one great quality in the flute and it is its complete surrender. There is nothing left in the flute and there are no residual desires. In fact, the inside of the flute is completely hollow. The flute has nine holes in it and the flute of our body has also nine holes. That flute has been able to go close to the Lord because there is no pulp left in the flute and it is completely hollow. So also if we can remove all the pulp of desires from our body, then there is no doubt that this flute of our body can also go close to the Lord. (SSB 1974, p. 30)
( Flute in the hands of Krishna)
If you have the capacity to draw the Lord to yourself, He will come to you and be with you. Be like the flute, a hollow reed, straight, light, with no substance to hinder His breath. Then, He will come and pick you up from the ground; He will breathe divine music through you, playing upon with a delicate touch. He will stick the flute into His sash; He will press his lips on it. In His hand, the Infinitesimal will be transmuted into the Infinite, the anu will be transformed into the ghana. (S.S.S. Vol. IV - p. 81)
The flute in the hand of Krishna reminds all of the need to make oneself into a hollow reed, with no trace of the pith material greed. Become straight, empty yourself of all obstructing desires and the Lord’s breath will flow through you, making a sweet music that awakens every soul. (S.S.S. Vol. IV - p. 186)
The gopikas realised that the song of the flute is identical with the song of Veda. When we are able to convert this human body which has nine holes into a flute which also nine and make it function like a flute, we will be able to hear the divine song. (SSB 1974, p.212)