Just think of it as music

No Instruments? For Pentatonix, It’s No Problem
November 06, 2013
http://www.npr.org/2013/11/07/243213446/no-instruments-for-pentatonix-its-no-problem

They start with a beat, then add in the bass.
After layering the harmony on top of background vocals, the solo shines on top — you wouldn’t even know there weren’t instruments being played.
Named for the pentatonic scales, Pentatonix is a five-person singing group that formed to compete in the NBC a cappella competition show The Sing-Off.
Three of its members were friends from high school, but the full group met for the first time just hours before the show to rehearse. Pentatonix ended up winning the competition, as well as the record deal that came with it.

“We try to do it in a way where you don’t think of it as vocal music; you just think of it as music

this I believe: Brian Eno

this I believe
Singing: The Key To A Long Life
by Brian Eno
November 23, 2008
http://www.npr.org/templates/story/story.php?storyId=97320958

I believe that singing is the key to long life, a good figure, a stable temperament, increased intelligence, new friends, super self-confidence, … and a better sense of humor. A recent long-term study conducted in Scandinavia sought to discover which activities related to a healthy and happy later life.
Three stood out: camping, dancing and singing.

psychological benefits: Singing aloud leaves you with a sense of levity and contentedness.
And then there are what I would call “civilizational benefits.” When you sing with a group of people, you learn how to subsume yourself into a group consciousness because a capella singing is all about the immersion of the self into the community.
That’s one of the great feelings — to stop being me for a little while and to become us. That way lies empathy, the great social virtue.

You want songs that are word-rich, but also vowel-rich because it’s on the long vowels sounds of a song such as “Bring It On Home To Me” (“You know I’ll alwaaaaays be your slaaaaave”), that’s where your harmonies really express themselves. And when you get a lot of people singing harmony on a long note like that, it’s beautiful.

the other thing that you have to harmonize besides pitch and rhythm is tone.
To be able to hit exactly the same vowel sound at a number of different pitches seems unsurprising in concept, but is beautiful when it happens.

Eno’s Group-Sing Song List:

Can’t Help Falling In Love (Elvis Presley)
Love Me Tender
Keep On the Sunny Side
Sixteen Tons (Tennessee Ernie Ford)
Will the Circle Be Unbroken
Dream
http://en.wikipedia.org/wiki/Dream_(song)

If I Had a Hammer
Love Hurts
I’ll Fly Away
Down By the Riverside
Chapel of Love
Wild Mountain Thyme
Que Sera, Sera

Cotton Fields

related:
https://franzcalvo.wordpress.com/2013/06/09/imperfect-harmony-how-singing-with-others-changes-your-life