Bishop Wilberforce's Unsolved Riddle

Thought you guys might enjoy this — an unsolved riddle from the 1800s. Story and contents of puzzle have been copy pasted from here:

Bishop Samuel (“Soapy Sam”) Wilberforce, who once famously debated Charles Darwin’s protege Thomas Huxley — Darwin himself was slated to debate Wilberforce but got sick and sent Huxley in his stead — was, among other things, about the most forceful public speaker of his day.

The writer Benjamin Disraeli coined the unforgettable “Soapy Sam” sobriquet, because the Bishop’s manner was, according to Disraeli, “unctuous, oleaginous, saponaceous.”

In addition to being a brilliant speaker, Soapy Sam was also a man who enjoyed a good riddle.

He was born in September of 1805 and died in July of 1873. After his death, the following was found among his papers:

I’m the sweetest of sounds in Orchestra heard,

Yet in Orchestra never was seen.

I’m a bird of gay plumage, yet less like a bird,

Nothing ever in Nature was seen.

Touch the earth I expire, in water I die,

In air I lose breath, yet can swim and can fly;

Darkness destroys me, and light is my death,

And I only keep going by holding my breath.

If my name can’t be guessed by a boy or a man,

By a woman or girl it certainly can.

I have no idea what it might be. Any guesses?