The phenomenon has been thoroughly documented and explored in Mark Cocker's fantastic 'Crow Country', which I heartily recommend. Having observed it several times last winter I look forward again to the sight again this year. This short film culled from footage I shot last year cannot convey the awesome spectacle or indeed sound, but I hope gives some taste of the scale.
I wrote the music as a response to this experience. For me there is a sense of foreboding and high drama about the spectacle, which I tried to reflect. I made no attempt to imitate the actual sound, instead drawing inspiration from the mix of sounds; the deep organic chatter of the rooks mirrored in acoustic guitars whilst referencing the higher, almost electronic noises of the jackdaws, using a theremin.