When Francis Galton was 85 years old, he went to a country fair where there was a contest to guess the weight of a prize specimen of livestock. Galton loved getting his hands on data, which was far less abundant a century ago, so he tabulated all the slips upon which entrants had written their guesses. His initial assumption was that this would show what bad guessers random people are, but it proved the opposite. The average guess was quite close to exactly right. This became known as the Wisdom of Crowds. (How many other 85-year-olds have come up with a significant new concept that contradicted their initial impression?)

You can see something similar with a crowd singing. A crowd derisively chanting "Air-ball!" at a basketball game will hit the two notes well. The errors cancel out. (Of course, it helps that some people who know they can't carry a tune will lip-sync so that their friends will assume they are singing along correctly. Not me, of course, but I have a friend who does this.)

Here's a press release type article from 2008:

Despite the hilarity of early-season "American Idol" episodes, nearly everyone can carry a tune, new research shows.

Of those who can't, there are two types — those that know they sound bad and those that think they sound fine.

In a series of studies led by researchers at the University of Finance and Management in Warsaw and the University of Montreal, more than 150 people in Canada and Poland were asked to sing familiar songs — such as Quebec's version of "Happy Birthday" – as a capella solos. In the final study, 40 people were also asked to sing isolated notes after hearing them played once.

To control for self-selection, the majority of subjects were initially unaware the study would involve singing. While none balked at the task, many joked about having a terrible voice.

They needn't have worried. The researchers found that more than 90 percent of the participants could sing in tune.

Okay, but there's probably a Darwinian winnowing of which songs get to be universally sung and thus included in this study. I don't know what Quebec's version of Happy Birthday sounds like, but America's version of Happy Birthday is popular in part because it's easy for 3-year-olds to sing. In contrast, Bacharach and David's "I Say a Little Prayer" would never become universal because you pretty much have to be Dionne Warwick or Aretha Franklin to get through the chorus without running out of breath.

And almost 100 percent nailed each melody's timing.

The results, most of which are detailed in the February 2007 issue of the Journal of the Acoustical Society of America, will be presented July 2 in Paris at the largest ever meeting on the science of acoustics.

Among out-of-tune singers, lead researcher Simone Dalla Bella explained, "there are two categories of people." The majority is tone deaf; they can't hear when a note is off and have no idea they are singing poorly. But there are also lousy singers with great hearing ability — those who can accurately say whether an instrument is properly tuned or a sung note is off-key. These squawkers know they are singing badly but, for some unknown reason, cannot correct themselves. They are, in a sense, tone mute. ...

I'm a little (or a lot) of both. I can usually approximate the first three to six notes of, say, "Old Man River," but then, inevitably, something goes noticeably wrong. But even if I get through a line in a manner satisfactory to my ear, when I ask my wife to sing it, it immediately becomes evident to me that I had only had a coarse notion of the melody in my head (usually, my notion of how to sing a song is something like "Start in the middle, go up, then down, down even more, up a little ...)

On the other hand, I can notice quite well when a bit of one song is lifted from another.

"I am not saying that most people are as good as professional singers in every task," Dalla Bella explained. The studies measured pitch and timing, but not timbre or musical expression. Also, many recreational songbirds are only in-tune when singing slowly.

The popularity of "auto-tuning" among pop superstars today suggests that the ability to sing really well is not super widespread. In particular, staying on one key throughout a live performance of a song is not easy, even for top amateurs, such as American Idol finalists. And, among the judges, only Randy was sure to notice a single lapse in key.

Evolutionarily speaking, carrying a melody's timing may be more important than its tune. Singing as a group is popular in cultures worldwide, and researchers hypothesize that singing together strengthens social bonds. While crooning off-key can be muffled by other voices, belting out when everyone else pauses is sure to garner unwanted attention.

I hate it when everybody in the audience starts to clap along with the song. I have to look out of the corner of my eye and watch my neighbor to avoid embarrassing myself. Oh, wait, that's not me, that's a friend of mine who does that, the poor bastard.

I have a theory that a sense of rhythm is pretty much crucial for success in arts and entertainment, not just in music, dance, and comedy but perhaps even in media as far afield as political rhetoric, literature, or even drawing.

I wonder which celebrities don't have much rhythm or timing? Vince Vaughn comes to mind as an exception that supports the tendency, but maybe he has some genius sense of rhythm that I just don't get.