Eric Whitacre

Wikipedia (1970-present) [US. Modern.]
If you're just gonna listen to one: A Boy and a Girl (Polyphony)
[Or two: Water Night (Polyphony) - this piece is broken into up to 14 voice parts at times... Well, actually just once, but it's a very lush chord about halfway through the song.]

Background

Eric Whitacre and I graduated from college in the same year. So he's youngish, at least compared to the other people I've written about in this blog. He's written music for wind ensembles (most recorded: Ghost Train), but it's his choral music that gets the most attention and performance.

Choral Music

Sleep (Polyphony)
Cloudburst (VocalEssence & St. Olaf Choir)
Leonardo Dreams of His Flying Machine (University of Santo Thomas Singers)
Nox Arumque (VocalEssence & St. Olaf Choir)

Whitacre is probably most known for his creation of the Virtual Choir. He has done three of his own compositions with virtual choirs, and the project has grown with each iteration. Here are the Virtual Choir renditions of those songs:

VC1: Lux Arumque - 185 voices, 12 countries
VC2: Sleep - 2,052 voices, 58 countries
VC3: Water Night - 3,746 voices, 73 countries

Whitacre was also featured in a TedTalk about his Virtual Choir project...