We've all seen the EQ setting in iTunes, but not many of us know exactly how to use it to its full potential. Rich Tozzoli, Senior Editor of Surround Professional Magazine breaks each EQ slider down and helps you get the most out of your music.

For those of you who want a little more, or a little less of your music in iTunes , there is a handy built in equalizer lurking behind the screen.

This type of EQ is called a graphic equalizer, because the selections of frequencies are laid out in a straight line. To be more specific, it's called a 10-band graphic equalizer, since there are 10 different EQ frequencies (bands) to choose from. A 10-band graphic EQ is slightly different from a typical stereos' EQ, which might have just a fixed treble and bass setting. For example, when you do turn up the bass, you'd be increasing only one set frequency usually around 100 Hz (hertz). The same applies if you turned up the treble knob, which might be set to 10K (kilohertz).

The benefit of the graphic 10-band EQ in iTunes is that you have the choice over which band you choose to increase, or decrease. iTunes has frequency choices at 32, 64, 125, 250, 500, 1K, 2K, 4K, 8K and 16K (which again stands for kilohertz). These various bands will have differening effects on the sound of your music. In the EQ window, let's start from left to right and quickly discuss what each band does.

Let's start from left to right on the EQ and quickly discuss what each band does.

32 Hz: This is the lowest frequency selection on the EQ. This sits in the lowest of low bass frequencies, where sub information resides in mixes –such as kick drums and bass instruments. Some speaker systems can't even reproduce this frequency.

64 Hz: This second bass frequency starts to become audible on decent speakers or subwoofers. Again, mostly bass drums and bass instruments will reside in this region.

125 Hz: Many small speakers, such as in your laptop, can just about handle this frequency for bass information. In other words, if you turn it up on most systems, you'll hear more bottom in your mix.

250 Hz:  This is still considered low-end, but more of the "woofy" sound of bass and drum sounds. Guitars and pianos will have a large amount of low end in this frequency range.

500 Hz: Now were approaching midrange frequencies, but still some of the low end of vocals and the mids of bass instruments sit here in a mix.

1K: This is now low midrange of most instruments such as guitars, pianos, snare drums, etc.

2K: The 2k frequency can boost or cut the "nasal" sound of your music, in the range your voice makes when you hold your nose and talk.

4K: 4k is the upper mid range that many electric guitars sit in, as well as a large portion of many instruments.

8K: This is getting into the high end, where the majority of cymbals and hi-hats are, as well as upper range of synths, pianos and guitars. Many vocals have a lot of information in this range.

16K: Theoretically, us humans can hear just above 20K, so this is true high end. If you crank this up, your mixes will get ‘sizzly'. This is the top of high end on the iTunes equalizer.

If you click and hold down the drop down menu at the top of the 10-band graphic EQ (now that you already know what that means), you can choose Presets for various types of music, such as Electronic, Jazz, R&B and Rock. If you choose "Electronic" for example, you'd see most of the frequency bands on the EQ boost up, especially the lows and highs. This will have a noticeable effect on your music, increasing the amount of low end and high-end information in the music. If you chose "Treble Reducer", it will do just that – lower the 1K thru 16K bands, therefore reducing the high end. A preset like "Loudness" boosted most of the low end, cut some 4K, and really turned up 8K, with only a slightly larger amount of 16K. If you do that, your music will seem, well… louder!

You can also make choices in the drop down menu to edit your presets by renaming or deleting them, or you can choose to Make Preset. This lets you save your favorite settings after you've moved the EQ bands up or down. I have many different settings I've saved, usually after calling up a Preset and changing it to my liking.

The only other choices on the Equalizer are the ability to turn on or off the EQ by selecting "On", and a variable Preamp slider. The Preamp will bring up the overall gain of iTunes, which is almost like turning up your volume on your stereo system. Be careful though, because by turning up a preamp too much, you can overdrive your system, which creates a nasty, crunchy distortion (unless you like that kind of thing). By turning it up just a little, you can certainly get more volume out of your speakers. Combine that with some of your own 10-band graphic EQ settings, and the Equalizer can be quite a powerful tool!

Depending on your tastes, you may want a different EQ setting for each artist, album, genre, etc. iTunes actually lets you assign a preset to each individual song but you probably don't want to get that carried away.

Award winning producer/engineer/mixer Rich Tozzoli is also a columnist for such publications as Pro Sound News and Digidesigns' DigiZine. A specialist in 5.1 surround sound, he has worked on DVD's for such artists as Carly Simon, Blue Oyster Cult, Billy Squier and David Bowie.

Special thanks to the following people for their comments: N. Ziarek, and David Ondrick.