Do You Hear What I Hear?

I was listening to Christmas music in the car and felt all warm inside as the oh-so-familiar voice of John Denver filled my car with fond memories.  It made me happy!  It took me back to my childhood Christmases.  But who is that singing with him?  I know that voice, too.  Who is that?!?!
I love Christmas music.  All of it!  It actually makes me feel sad when people say they hate Christmas music.  How can you say that? Hate is such a strong word and "Christmas music" is such a broad topic ... it just makes no sense to me for someone to say they hate it all.  I mean, really, the only person I would expect to say that is Bob Humbug.  Or the Grinch. Seriously.
I love it all.  I love the oldies and the new stuff.  The serious and the silly.  I love Nat and Bing and Andy Williams.  I love how Dean Martin sounds more than a little tipsy (and a bit like a leprechaun) when he sings about Rudy the Red Nosed Reindeer.  I even love to dislike poor little not-so-naughty Eartha who got nothing for Christmas because she wouldn't put out. 
I just need to figure out who is singing with John Denver .... ?
I love it when they take me to church.  I'll drive down every gravel road in the tri-state area trying to sing Silent Night like Stevie Nicks.  When Whitney wants to know if I hear what she hears .... I hear it, girl, I hear it.  When Mariah Carey tells me to fall on my knees, I truly feel compelled to do so.  And when Rod and Mary J. start crooning about the three kings, Lawd, I'll raise my hands right up to Heaven whenever I hear that beauty.  Which may not be a good thing since I usually hear it while I'm driving.
But who is singing with John Denver?
I love the silly songs, the meaningful songs, I even love the slightly disturbing songs ... "Say?  What's in this drink?"  I love that they make me laugh, and cry, and smile. Sometimes I feel pangs of nostalgia.  Whenever I hear "It's Christmastime in the City" I remember the Christmases I spent in Madrid where a local shop owner tried to convince me that in Spain, there is no Santa Claus.  What?!  He said, "No.  In Spain it is really the Dad."  When I hear Aspenglow I always think of snowy car rides getting to and from "Christmas" in South Dakota.  And no matter who sings The Little Drummer Boy, I remember moving the needle on an old record over and over until I knew all the words by heart.
I don't care if they sing about Santa, or the Little Baby Jesus, or presents or snow or lights or shoes or teeth .... I love them all. 
I just need to know who is singing with John Denver!!!
Wait!!!
I totally know that voice.
I know it!!
It's Kermit the Frog!!!