I think it's one of the most beautiful pieces of jazz ever composed. Listening to it is like watching snow through a window. The room is warm, something is roasting in the oven, and outside the flakes are falling faintly through the universe and upon the trees, the hedges, the rain gutters, the telephone poles, and the rooftops of a thousand apartment buildings in a very big city. This is where you want to be forever. This is Vince Guaraldi's "Christmas Time Is Here." It opens with a trembling bass, like someone coming out of the cold, stamping their feet, brushing the snow off their shoulders, hanging up their winter coat, rubbing and blowing on numb fingers, and entering the living room where there is a window for watching the flakes falling faintly upon all the buildings of the living.

"Christmas Time Is Here" is the centerpiece, in my opinion, of the soundtrack for the masterpiece of American culture A Charlie Brown Christmas. It was composed by the Bay Area jazz pianist Vince Guaraldi. It first appeared on television on December 9, 1965. It forever married jazz with Peanuts, a comic strip by Charles Schulz. But the story of how Guaraldi's music and Schulz's characters came together is filled with accidents.

The Golden Gate Bridge figures into it. As does the jazz DJ Al "Jazzbo" Collins. As does a documentary about the black American baseball legend Willie Mays. The more you look into the story of the soundtrack of A Charlie Brown Christmas, the more the idea of a God with a master plan is erased and replaced by the story of chaos.

I'm walking to the house of the local jazz pianist Jose Gonzales. There's a lot of wind, but the leaves on the sidewalk are wet. The clouds are low. And though it is 11 a.m., it looks like the day is already about to be done with. Hillman City is behind me, and Seward Park ahead.

For the past six years, Gonzales's trio—with Michael Marcus (bass) and Matt Jorgensen (drums)—has been performing the entire A Charlie Brown Christmas to raise money for Strawberry Theatre Workshop. (Taproot Theatre, the Royal Room, and Fremont Abbey are also producing performances of it this year.) Gonzales, who was born in Arlington, Washington, and was trained initially in classical music, knows this soundtrack inside and out.

I'm visiting him because I want the power of the music revealed to me. What makes it right as rain for Peanuts? Why Guaraldi and not someone else? Exactly what made him the best possible pianist for the comic strip in this of all possible godless worlds?

Gonzales welcomes me into his home. He is wearing cozy purple slippers. The piano is in the center of his living room. He shows me a seat (I take it), and, without wasting time, he sits at the piano and begins to explain.

"The first thing you have to understand is that, culturally, when this soundtrack is released, jazz is still popular. Nowadays, it's not. But back then, it is the thing. This is the mid-1960s. And if this popularity wasn't there, then most likely the music would have been something silly or even slapstick-ish. So you have that."

He went on: "But also remember, Guaraldi was not the first pick. It was actually Dave Brubeck. And also remember, the music was first composed not for the Christmas special but for a documentary."

In 1963, Lee Mendelson, a TV documentary filmmaker, got the strange, possibly brilliant idea that, after making a successful documentary about the greatest baseball player ever, Willie Mays (A Man Named Willie Mays), he would make a doc about the worst one ever, Charlie Brown (A Boy Named Charlie Brown). He contacted Schulz about the idea of a documentary about Charlie Brown, and Schulz said he was down. But then Mendelson, a huge jazz fan, needed the right music for the doc. Who had the right sound for the kid-world of Peanuts?

"Mendelson begins looking for someone to score the documentary on Charlie Brown," explains Gonzales. "His first choice is Dave Brubeck, but he turns down the offer because he's too busy. He's flying high from 'Take Five.' Brubeck recommends the vibraphonist Cal Tjader, but he's too busy too. So Mendelson is in a cab crossing the Golden Gate Bridge. The driver is listening to Al 'Jazzbo' Collins's jazz show. Collins plays 'Cast Your Fate to the Wind.' It's Guaraldi's biggest hit at the time, and Mendelson thinks: 'That's the sound I'm looking for. That's it.' This is what he heard on the bridge..."

Gonzales plays "Cast Your Fate to the Wind" on the piano. "You can already hear the Peanuts in this music. Melodically it is complicated, but it's also open and accessible. The [Christmas special] does not sway too far from that sound." Mendelson eventually contacted Guaraldi, who was at Fantasy Records, and they met for lunch at an Italian restaurant, Original Joe's, in North Beach, San Francisco. Guaraldi took an immediate interest in the project because he was a fan of the comic strip. Soon after the lunch, Guaraldi became a part of a documentary that went nowhere. After it was completed, no one wanted to air it on TV. The doc was too weird or something.

But in 1965, the soft-drink corporation Coca-Cola called Mendelson about producing a Christmas special. Other corporations, like General Electric, had sponsored hugely successful TV Christmas specials, like the nightmarish stop-motion animation Rudolph the Red-Nosed Reindeer, and Coca-Cola wanted a piece of the action. Mendelson pitched A Charlie Brown Christmas off the top of his dome. Coca-Cola said they were down. What followed became an important institution in the cultural history of the United States.

"During the performance of A Charlie Brown Christmas, I try to play as much of Vince as I can," Gonzales says as he plays the opening track, "O Tannenbaum." "I'm trying to stay true. But I do do my own interpretations." Gonzales has also released a CD, Linus and Juicy: A Holiday Album, based on the music of the show.

"Hear that great interior movement. That's jazz. In general, you want to keep the transition within a certain distance, because the ear wants to hear things slide and slide. Vince does this so well."

I feel more than understand much of what Gonzales is saying. "He does this descending thing, which leads the ear to the next thing," he says while playing "My Little Drum." "And here he goes into the jazz. And here, you can do whatever you want. But he throws in a little blues lick to bring you back when he goes a little out there. But I do like taking it more further out there than Vince."

Gonzales then describes the love of my life, "Christmas Time Is Here," step by step. Despite his technical language, the beautiful music can still be heard. It's like looking at a mathematical formula and hearing Gabriel Faure's "String Quartet in E Minor" rise from the dense combination of numbers. "It's just gorgeous," says Gonzales, who is now in the meat of the song. "It's perfect for this kind of cloudy day. But what's great about the song is it's actually appropriate for any time of the year. It's not really just for Christmas."

Though this is strictly true, I listen to the song only in the last two months of the year. Same goes with reading James Joyce's short story "The Dead," which is a Christmas story set in Ireland and ends with snow falling through the universe. I can read "The Dead" only in November or December. I do not want to hear "Christmas Time Is Here" in the middle of summer. I want to feel its beauty when the red and gold leaves are falling, when the days are short, when a little snow taps on the windowpane.