This has been rumbling around on YouTube for a couple of years now so you may already be aware of Eric Whitacre. But if you have not heard of him, take a few moments to look at the attached videos.
He is a Nevada-born fella who is a Grammy-winning composer and conductor - a contemporary musician of great skill. He is a lecturer of choir work-shops that I would pay good money to attend - and while in no way downplaying his skills and talent, it must be said that from a truly shallow point of view, he is also very easy on the eye too!
Only in this YouTube and digital age could he have come up with such an inspired way to make music.
Look at this for an idea of how a Virtual Choir works.
And then watch this link to see it all come together.
Bloody fantastic if you ask me.
Signed off by a very self-doubting and amateur alto!