Kundalini and inner sound of birdsong

[mandala]

Back in 2007, in the Himalayas, I practised Moola Bandha in my room, alone. That night I awoke and could hear a bird singing - but 'I' wasn't listening to the bird singing 'I' was the birdsong....

I also experienced the whole back of my skull feeling 'open'

I have no teacher and so my process of understanding this has been a long one - only from books/Internet but I believe the sound of the bird is an inner sound or nada. I previously thought that the bird had been outside the window at the time, until I came across the description of birdsong accompanying a mooladhara awakening.

Can anyone confirm this, and with references?!

Thanks.

[michaelangelo7]

Hazrat Khan "It sounds like Thunder, the roaring of the Sea, the jingling of Bells, running of Water, the Buzzing of bees, the Twittering of sparrows, the Vina, the Whistle, or the sound of Shankha..."(The Mysticism of Sound)

Madame Blavatsky from the Voice of the Silence, on the nadas : "The first is like the nightingale's sweet voice chanting a song of parting to its mate.  
The second comes as the sound of a silver cymbal of the Dhyanis, awakening the twinkling stars.  
The next is as the plaint melodious of the ocean-sprite imprisoned in its shell.  
And this is followed by the chant of Vina.  
The fifth like sound of bamboo-flute shrills in thine ear.
It changes next into a trumpet-blast.  
The last vibrates like the dull rumbling of a thunder-cloud"