Judges, left, Randy Jackson, Paula Abdul, and Simon Cowell will help America choose the next "Idol."

By Larry Carroll
Special to MSN Entertainment

Every new year brings with it hope. The hope of world peace, of good health for friends and family and, naturally, renewed hope for thousands that they'll make it through the nationwide auditions to become the next "American Idol."

This year's process has already begun, and Season 7 launched Jan. 15. But, if you're among the few and the chosen, are you really ready for prime time? Based on the fact that the same judges, and the same die-hard millions who've powered "Idol" in the past, will be returning once again, the time has come to start looking for patterns.

Gallery: See photos of "Idol" hopefuls

So sit back, rest those vocal cords with some herbal tea, and read on. Because if you're going to become Season 7's big winner, you'll definitely want to hit these notes.

Don't Dance
Every season, a few early wannabes attempt to augment their performance with dancing. Most are dismissed immediately, and for good reason: If you feel the need to dance, then you must know you can't sing. America learned that the hard way with Britney Spears, so why should they have to do it all over again with you? Occasionally, once a contestant like Taylor Hicks has established the power of his pipes, he'll dance and get away with it. Other times, a Joshua Gracin or Jon Peter Lewis kicks up his heels and quickly gets the boot. Either way, it's just not a safe bet, folks. If you want to dance, go on that Marie Osmond show.

Dog Is Your Co-Pilot
America loves an underdog. So, if you're ugly, overweight, got picked on as a kid, or simply suffer from the occasional zit, play up your perceived handicap. As your singing skills get asserted, you can evolve into a more photogenic version of yourself (Hi, Clay Aiken. Hi, Elliott Yamin!), and the fans will rally behind you.

Check Yourself Before You Wreck Yourself
Embrace the point above, but just beware that if your underdog gets too big for its collar, the voters won't hesitate to send you to the doghouse. Everybody loved Chris Daughtry -- until he started getting cocky. And don't snap back at the judges, a la Justin Guarini, Julia DeMato or Brenna Gethers -- it'll just make you look like the over-egoed second act in a bad musical biopic. Believe it or not, the audience really does like Simon, Paula, and Randy, and have come to regard them like family -- so, if you get too big for your britches, you'll be booted out like a drunken uncle at Christmas.

The South Shall Rise Again
If you're from the South, get thyself to an "AI" audition, post-haste. Don't laugh: It worked for winners Kelly Clarkson (Texas), Ruben Studdard (Alabama), Fantasia Barrino (North Carolina), Carrie Underwood (near the Oklahoma and Arkansas border), and Hicks (Alabama), as well as runners-up like Clay Aiken (North Carolina), Diana DeGarmo (Georgia) and Bo Bice (Alabama). There seems to be several reasons why people from Los Angeles and New York never win: they're too polished, they lack Southern charm, maybe they just don't appeal to the Wal-Mart crowd. Regardless of whether any are true, the trend is clear: Start talking like Andy Griffith, or just stay home.

Pick Popular Songs
Just because you're from the South, doesn't mean you should perform country music -- and, no matter where you're from, don't dare sing a showtune. Showtunes sank the likes of Lisa Tucker and Mikalah Gordon. And Kellie Pickler and Bucky Covington's love of country didn't put them over the top, either. The judges seem to fall for rock music more increasingly with each passing year -- hence Daughtry, Bice and Gina Glocksen -- so, when it comes to the all-important job of picking your songs, skip Streisand and instead go for some Steve Miller.

Don't Be a Freak
Every season, America has an ill-advised one-night stand with Sanjaya and his mohawk, William Hung and his bangs, or Blake Lewis and his beatbox. If your plan is to rely on a fad, you're just trading 15 minutes of fame for a lifetime of mockery. If you really feel the need to go down that road, do like so many before you and simply make a sex tape with Paris Hilton.

Don't Be a Skank
While we're on that topic, short skirts, hot bodies and flirting with the bosses  will only get you so far on "American Idol" (unlike in the real world, where it gets you a corner office and an expense account ). Over the years, we've watched Haley Scarnato ineffectively show her skin, and let's not even get started on Jessica Sierra. Frenchie Davis' dirty pictures got her the boot, and Antonella Barba similarly blew her chances. When Corey Clark (allegedly) took flirting to the next level with Paula, it still didn't take him to the top. Learn from the past: Sleeping with Paula didn't do wonders for Emilio Estevez's career, and it won't help yours, either.

Don't Ring in the New Year
Like it or not, America is more likely to fall in love with you when you're single and ready to swing. Performers like Scarnato started the process with a significant other, then shed the baggage as time went on. If you happen to be wearing an engagement ring, it might be a good idea to hide that rock, and hope it puts you on a roll.

Gain a Few Pounds
Typically, traditionally good-looking people are lucky if they make it beyond the top 12. Underwood is the only "AI" winner who could possibly make it as a model, and both she and Clarkson were still burdened by a lot of baby fat when they took home the title. Once again, it proves that people like the underdog, and our supersized nation wants to see its own reflection in an Idol. So, don't look as though you could make it without the world's most famous reality show, or you just might have to.

If You Haven't Got the Talent, Stay Home
The bottom line is, the cream rises to the top, and this show carries on for so many weeks, in front of so many millions, that it always screens out the weaker members of the herd. So either bring your A-game, or sit home on the couch with a lap full of nachos, and join the rest of us in a state that's truly American: idle.

In this series, we’ll try to de-mystify some engineering terms by using something familiar to many of us: the acoustic guitar.

Formulas: Who Needs ‘Em?

You know, it’s amazing the reaction some people have when they have to solve, or in some cases “memorize” a formula—they’d rather scrape gum off the sidewalk than go through the math.

Hey, don’t fall into that trap! Formulas are the magic key to the kingdom. Sometimes the simplest formula holds the secret to understanding how something works…why an airplane can fly or why your skateboard flexes without breaking. Of course developing the formula is just the start. Once you “get” what the formula is trying to tell you, you might even be able to improve the design—the design of a car, a radio, a windsurfer or a guitar.

The word “guitar” in the title of this article should give you a clue as to which one of these systems we’re going to use as an example. It will be an ACOUSTIC guitar…one with nylon strings.

By the way, if you really understand what a formula’s trying to tell you, ‘memorizing’ becomes trivial. Understanding and deduction are great memory aids.

The CHALLENGE:

DERIVE THE FORMULA FOR THE FREQUENCY (PITCH) OF A GUITAR STRING.

There are a couple of ways we could do this. One is to delve into the mathematics of vibration, looking at the variables surrounding the string. This answer is readily available in physics textbooks.

The more interesting way, one often used by practicing engineers, is to just try a few things. You might accidentally get the answer, and you might even learn something along the way. THEN you can go back and verify the answer with math. Yeah, you still need to be able to handle the math, but this way it will feel much easier.

Let’s start by examining an acoustic guitar. What can you tell just by looking at it?

• It has strings. Usually 6 of them, each with a different pitch.
• Each string looks a little different from the other. Some are larger in diameter than others; some look like they’ve been wrapped with wire.
• There are geared pegs at one end of the guitar.
• There are frets on the guitar, dividing the fingerboard into regular intervals. These intervals seem to be geometric (not linear).
• The strings terminate at the bridge, and there’s a big hole in the top of the guitar.
• The strings are suspended on both ends by some form of plastic or bone, keeping them away from the fret board. One end is the “nut” and the other is the “saddle”, located on the bridge.

OK, that didn’t take a rocket scientist, and we can deduct a lot from our observation. [Hint: 90% of innovation in engineering is observing and being prepared to notice when something weird happens.]

GUESS
Now let’s take a GUESS as to what the formula might be. A GUESS? Sure. That’s how a lot of advanced math is done…guess at the form of the answer, and then verify it either by solving it mathematically, with equations, or empirically, by doing experiments. We’re going for the empirical route this time.

A formula has a DEPENDENT VARIABLE…the thing you’re trying to analyze (in our case, the string frequency). There are also some INDEPENDENT VARIABLES—things that affect the dependent variable. So our first guess is…

f = F {string length}* F{Some Other stuff}

That is, the frequency f is a Function of the length of the string and some other independent variables. The first part should be a pretty easy “win” for us…after all, that’s why the frets are on the guitar.

Pluck the low E string without touching it with your other hand. The E string is the largest string, the one with the lowest pitch. When you don’t push down on any frets, it’s called an open string. Now push the same string down to any fret and pluck it. Does the pitch (frequency) go up or down?

The answer’s pretty obvious: the pitch goes up as you use frets that are closer and closer to the bridge. That means the frequency is INVERSELY proportional to string length. In other words, the shorter the string, the higher the pitch. Oops…that means our first guess was upside down. Let’s change it to…

f = F {1/string length}* F{Some Other stuff}

OK, so we know somehow it’s proportional, but is it a linear relationship? Let’s find out by halving the length of the string, and measuring the frequency. If it’s linear, the frequency should double. Find the fret that’s located where the guitar body meets the neck. That’s usually the 12th fret. What we’re after is the place where the string is exactly _ of its “open” length. Push down the string against this fret and pluck the string. What do you hear?

We can either test this with a frequency meter or an oscilloscope, or in this case, we can simply listen.

It turns out that, at the halfway point, the frequency of vibration is exactly TWICE that of the open string. In musical terms, this is one OCTAVE higher. The term ‘octave’ comes from the fact that eight musical steps are required to get from one note to its equivalent higher note: ABCDEFGA. Logically, I count only seven steps in this sequence, but musicians also count the note they started on. [I know, it sounds crazy to me too, but I’m an engineer, not a musician.]

We now have our first relationship with some certainty. The frequency is inversely proportional to the string length, and we can prove it’s linear by dividing the length into fourths, etc. Indeed, it is a linear relationship. So…

f = {1/string length}* F{Some Other stuff}

Pretty cool. And so far, we haven’t opened a math book, although we’ll do that later.

POSITION
What about the place where the string is mounted? Does that change anything? This may not seem logical, at first, but who knows?

Let’s experiment by using a tuning fork. As the two tines of the fork move back and forth in sympathetic vibration, the fork produces a fairly pure sound of known frequency. To tune guitars, most musicians use a fork tuned to an “A” note at 440 Hz.

Strike the tuning fork (not on the guitar!), and put its base against the neck of the guitar. What happens? Now strike it again and try it against the side of the guitar. And the back. And the top.

It’s pretty obvious that the volume of the sound increased dramatically when you put the tuning fork near the bridge on the top of the guitar. It's almost like having an amplifier built into the guitar. Looks like there’s a reason they chose that spot for the bridge. By touching the tuning fork to the top of the guitar, we get the whole top vibrating at the frequency of the fork.

OK, so we didn’t expect the pitch to change with location, but one thing happened that would not have happened if we just played with the math—we learned something extra. Guitar makers have long known that the top, or soundboard, is the most important component of the guitar. In fact, some very good acoustic guitars are constructed with the back and sides made of plastic, but with the top made of the best wood available. One famous guitar maker even created a guitar with a back made of papier-mâché, just to prove the point. It made a pretty decent sound.

TENSION
The tuning fork diversion was fun, but it didn’t get us any closer to deriving the formula. Now let’s go for the obvious “independent variable”--tension. We might guess that the tuning pegs have something to do with tuning the guitar (duh!), in other words they have a direct impact on the string’s frequency. What happens when you crank the tuning pegs to put more tension on the strings? Does the pitch go up or down?

Sure. With more tension, the frequency goes up. So…

f = {1/string length}* F{Tension + Some Other stuff}

That is, the frequency (pitch) is proportional to tension and inversely proportional to length.

Is it linear?
This one’s going to be a little harder to measure. We could stick a fisherman’s scale in line with the string, and pull on the string, but that would be inconsistent, not to mention scaring the guitar owner to death. But we can simulate a measurement by hanging something heavy from a guitar string that’s exactly the same length and type as the string on the guitar, as measured from nut to bridge saddle. Let’s do that.

Just get a broom handle, and either drill a hole through the broom, or wrap the guitar string so that you can rotate the broom handle and keep the length exact. The string length is about 65 cm, or about 24-26 inches for a standard guitar. Suspend a bucket from the other end of the string, and just start adding small weights until you get the right frequency when you pluck the string.

There’s a rule in experimentation: Only change ONE variable at a time. That’s why you have to keep the type of string and its length the same. The top of the bucket handle will be a pretty good “node”, which means you can do a pretty good job of defining the string length.

Now start adding weights, beginning with a 2-kg weight. Don't forget to count the weight of the bucket.

By the way, if you’re having trouble hearing the tone produced as you pluck the string, you could VERY CAREFULLY hold the guitar upside down against the broom handle, with the bridge just touching the handle. You’ll be amazed how much louder the note is.

What did you find? On my guitar, the tension was about 7 kg. per string. Think about that--multiply 7 kg by 6 strings, and that’s the weight of a sack of concrete! Now imagine suspending a bag of concrete from the face of that beautiful guitar. It must have taken a lot of experimentation (and more than a few tears) for the early guitar makers to come up with the right bracing to have the wooden top withstand such a force and still vibrate freely. The bracing is every bit as sophisticated as that of a highway bridge.

Fig 1. 7 kg X 6 strings = 42 kg. That’s roughly the same weight as a standard sack of concrete.

Want to have some fun? Attach a set of guitar strings to a closet rod. Then attach the other end to each of six separate wooden handles. Have one person hold the rod while six other people hold one string each. Pull on the strings until you have a tone that's roughly the same frequency as that of the appropriate guitar string. The poor person on the closet rod, who has to pull against all the other six strings, is in for a real workout. It gives you a good idea of how much force there is on the guitar's bridge.

If you have the luxury of using an oscilloscope to measure the frequency, you can create a plot of frequency vs. weight. What you’ll find is that the relationship is NOT linear. So…

f = {1/string length}* F{Tension + Some Other stuff}

…which is what we had before, but now we at least know that the formula is NOT simply {tension/length}.

MASS
One thing from our list is that the strings on the guitar look different. Some have a larger diameter, and others are wrapped with wire. Why is that?

Try this: Pluck the low E (6th) string. Now pluck the high E (1st) string. They should be two octaves apart in frequency.

Now loosen the tuning peg of the high E string such that it matches the frequency of the low E string. What do you notice?

Incredibly, what was once the high E string is now almost impossible to play. It’s too loose. It’s also extremely difficult to keep it in tune at the lower frequency. This must have something to do with the fact that the six strings are different. Let’s take another guess. The guess is that the mass of the string is important. We could create an engineering model for this system--let’s assume it looks like:

Fig 2. The model has two springs and a weight in the center.

In our model, the string is made of two springs, with a mass in the center. Let’s try it on the guitar.

Re-tune the high E string to its former pitch. (It should be the same pitch as the next string, when the next string is played on its fifth fret.) Now put a small piece of putty on the high E string. Something like tacky putty works, but it’s more dramatic if you use lead putty from a local fly-fishing shop. (You can buy it in the non-lead, or environmentally friendly version.) Put the putty exactly at the center of the string, typically on the fret where the neck joins the body of the guitar.

Strike the string very gently at the center, and see what happens to the frequency. Now strike the string just above the hole in the guitar top and notice what happens.

Fig 3: Adding some lead putty (center) to the high “E” string radically changes the acoustic properties of the string.

The result? The tiniest piece of lead putty not only lowers the fundamental frequency of the string, but it also has a devastating effect on the quality of the tone.

That explains it. Now we know why the strings are wound with metal wire. It’s to create a DISTRIBUTED weight system that evens the extra weight out over the entire string. The model should be more like this:

Fig 4: A better model distributes the weight all along the string. Distributed models are typically used to emulate complex devices like transmission lines.

That adds the last independent variable to our equation:

f = {1/string length}* F{Tension, Mass and maybe some other stuff}

In fact, if we open a physics book and do the math we’ll find the string frequency is:

This of course is a simplified equation. If you want to get picky about it, you can add effects due to temperature, barometric pressure, gravity and all kinds of other second-order effects, but the major items are here.

What does this equation tell you? It says:

• If we wanted to double the frequency (raise the pitch an octave) on all 6 strings, we would have to multiply the tension by a factor of FOUR. According to our weight experiment, that means about 168 kilograms of tension on the bridge of the guitar…roughly the weight of the average motorcycle. Hey, that’s too much for our thin wooden top, so either the guitar’s design would have to change radically, or we should look at changing the string mass instead.
• It’s pretty obvious that if we changed the length of the strings, we could make the guitar sound lower or higher in pitch. Indeed, that’s why a string bass is so tall and a mandolin is so short—their design is “tuned” to their octave range.

Well, we learned a lot by experimenting to find the answer. The hands-on approach taught us a few things that we would not have learned if we had simply focused only on the mathematics of string vibration. And, knowing what you now know about guitars, you might consider designing your own musical instrument. Let your imagination run wild. For example, how about making a string instrument that uses an entire building? You could suspend a huge diaphragm that looks like a drumhead on the ceiling of an auditorium, and connect a large cable to it. You'd have to figure out how to "pluck" the 30-meter long "string", but once you did the "instrument" would produce a sound too low in pitch to hear, but you could "feel" the sound once you were seated. It's your world. Explore it.

©2002
Agilent Technologies