Srimad Bhagavatam Canto 10, Chapter 21, Text 02

SB 10.21.2

kusumita-vanaraji-susmi-bhrnga
 dvija-kula-ghusta-sarah-sarin-mahidhram
madhupatir avagahya carayan gah
 saha-pasu-pala-balas cukuja venum
 
Translation: 
 
The lakes, rivers and hills of Vrndavana resounded with the sounds of maddened bees and flocks of birds moving about the flowering trees. In the company of the cowherd boys and Balarama, Madhupati [Sri Krsna] entered that forest, and while herding the cows He began to vibrate His flute.
 
Purport: 
 
As suggested by the words cukuja venum, Lord Krsna skillfully blended the sound of His flute with the lovely sounds of Vrndavana’s multicolored birds. Thus an irresistible, heavenly vibration was created.
Srimad Bhagavatam Canto 10, Chapter 21, Text 01
Srimad Bhagavatam Canto 10, Chapter 21, Text 03