CAN ANYONE SOLVE THIS?

I`m the sweetest sound in the orchestra heard,

Yet in an orchestra have never been.

I`m a bird of gay plumage `tho less than a bird.

Nothing ever in Nature was seen.

Touch the earth, I expire,

In the water I die,

In the air I lose breath,

Yet can swim and can fly.

Darkness destroys me, light is my death,

And I only keep going by holding my breath.

If I cannot be guessed by a boy or a man,

By a girl or a woman I certainly can.

Can you work this one out?