My Gurudeva writes:

In his kinkari svarupa Sripada Raghunatha is staying with Sri Radharani in Yavata as Syama
suddenly plays His enchanting flute in a distant forest. When She hears this flute sound Srimati Radharani is stunned. This flute sound is called snigdha or ardra (pleasant) and is full of love and flavour. This flute sound naturally makes everyone’s heart melt. It is not just called nada, or sound, but pranada, the best sound. This makes everything sweet.

This nectarean sound maddens all mobile and immobile beings. Srimad Bhagavata says aspandanam gatimatam pulakas tarunam, Krishna’s flute-song makes inert beings move and makes
mobile beings stunned. Streams of nectar emanate from each hole of this flute, along with a tune. One hole breaks Lord Brahma’s meditation, one hole causes the Yamuna to flow upstream, one hole causes stones to melt, and one hole revives the dead trees. The cowherds and gopis of Vraja all experience this Murali-song in their own way: yasomati sune bamsi nani de ma nandarani; pita nanda sune vamsi ei ye badha ani. sakhagana sune bamsi colo goshthe yai; kamalini sune bamsi bahira hao rai – “When Mother Yasomati, Nanda’s Queen, hears the flute she thinks it says: “Ma, bring Me butter!”, when father Nanda hears the flute he thinks it says: “Daddy, I’ll bring your shoes!”, when the cowherd boys hear the flute they think it says: “Come, let’s go to the meadows!”, and when the female lotus (Radha) hears the flute She thinks it says: “Rai (Radhika), come out!”

In these ways the flutesong is pranada, or the best sound for everyone, but especially for Radharani. When She hears it, She cannot stay in Her house anymore.