There's little room at the inn for new Christmas carols and songs.

Whether it's singing around the piano, caroling in the neighborhood or turning on radio stations with all-holiday formats, Americans sing and hear much of the same music they did a generation or more ago. In the past 30 years, only a few new holiday tunes have joined the likes of "Silent Night" and "Joy to the World" in the standard repertory or airwave rotation, including:

Paul McCartney's "Wonderful Christmastime" (1979).

Wham's "Last Christmas" (1984).

Mariah Carey's "All I Want for Christmas Is You" (1994).

Band Aid's "Do They Know It's Christmas?" (1984).

Adam Sandler's "The Hanukkah Song" (1994).

Not even country clubs have memberships this exclusive.

"A new holiday song has only six weeks of exposure, and it is competing with 50- and 60-year-old recordings," says Sean Ross, vice president of music and programming for Edison Research.

"New songs that do become entrenched do so over the course of years. Even a song like 'Wonderful Christmastime' is still considered new as far as Christmas songs go."

"It takes a special new piece to tap into that realm quickly," says Rebecca Rollett, an expert in lesser-known and older Christmas carols. "One of the newer carols to make it into the canon is 'White Christmas.' But those opportunities don't exist anymore. It is harder to get into the public consciousness."

So the formula is simple for a songwriter with a Christmas wish: Simply do like Irving Berlin and write a brilliant song such as "White Christmas" that becomes one of the top-selling singles of all time.

You might as well try to teach reindeer how to fly.

That's why artists for years have looked instead to covers of traditional carols, songs and hymns.

"It is so much easier to get an old Christmas song on the radio instead of a new one," continues Ross. "That's why every year you have a slew of artists who put out albums of the traditional tunes."

Bruce Springsteen's high-energy version of "Santa Claus Is Comin' to Town" is a shining example of how a new recording of a classic can deck its own halls. Artists from every genre have tried to capture that Santa magic: David Bowie, Josh Groban, RuPaul, the Brian Setzer Orchestra, Faith Hill, the Temptations, Jessica Simpson, Run DMC and many more.

"[Artists] tend to go with familiar songs," agrees Dan Michaels, program director of WLTJ (Q92.9), which takes on a Christmas format each season. "You see very few new ones. It is like comfort food."

If you go back 10 more years, you can include John Lennon's "Happy Xmas (War Is Over)" (1971) and Randy Brooks' "Grandma Got Run Over by a Reindeer (1978). You have to travel even further to catch a few more that have staying power: Albert Hague's "You're a Mean One, Mister Grinch" (1968) or the warm and homey jazz stylings of Vince Guaraldi's "Christmas Time Is Here" (1965) from "A Charlie Brown Christmas."

"Grandma" is typical of how long it can take a new tune to get its own Christmas stocking. Recorded by the duo Elmo and Patsy in 1979, it primarily got play on country stations until the group re-recorded it in 1982 and pushed it on Top 40 stations. Now the one-time novelty song is a Christmas standard.

"Every generation has the music they grew up with, and that gets passed on to the next generation," says Ross. "With Christmas music, it is cumulative."

And centuries of holiday music have built up a sizable and exclusive canon.

"The bulk of the most popular carols date from the 19th century -- 'Hark, the Herald Angels Sing,' 'Away in a Manger,' 'Silent Night,' etc.," says Rollett, who gathers a different batch annually for the Pittsburgh Camerata's special holiday concert. But there are many that are much older.

"The absolutely oldest carol or hymn that I can come up with is 'Of the Father's Love Begotten' -- with text written in the fourth century, and a tune from the 11th or 13th century, depending on who you believe," she says. "Not really a top-of-the-charts hit, though.

"An older tune would seem to be 'Conditor alme siderum (Creator of the Stars of Night),' which seems to be seventh century. Again, not one you would hear at the mall."

But there are several ancient carols that are very popular today, including "In Dulci Jubilo (Good Christian Men, Rejoice)" from around 1400; "O Come, O Come, Emmanuel" (text from the ninth century, chant melody from the 15th century); and "Coventry Carol (Lully, lullay)" from around 1500, says Rollett.

"What Child Is This?" is a case of new religious text applied in 1865 to the 16th-century folk song "Greensleeves."

So this Christmas, consider the plight of Neil Diamond. The singer-songwriter has just released a new Christmas album headed by a brand-new holiday song, "Cherry Cherry Christmas."

He may have risen to the top of the charts with "America" and "Sweet Caroline," but he has his work cut out for him when it comes to Christmas.

Critics Andrew Druckenbrod and Scott Mervis talk about music on "The Beat," available exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.