You would think an electric guitar could plug directly into a computer soundcard or interface in the same way keyboards and drum machines do, but it's not advisable for a couple reasons. First, even though the output of an electric guitar is, obviously, electronic and exits the instrument though a cord, the signal is much weaker compared to other electronic instruments. This is due to the guitar's pickups—the guitar's sound-producing devices that give the electric guitar its charm. However, they're just magnets and are fairly weak as far as generating a healthy electronic signal.

The second reason against plugging in directly is that an electric guitar uses the amplifier to help create the special character of its sound. Whereas a keyboardist uses an amp to simply magnify, without distortion, whatever was there in the first place, guitarists use their amps to provide the sound quality or color. An unadorned guitar sound, without the contribution of a guitar amp, is not a terribly useful sound from a musical perspective. Fortunately for guitarists, there are many fun and cool ways to fix this. The simplest and purest way to capture an electric guitar through a cranked amplifier—the way nature intended—is to stick a mic in front of the amp. Hearing an electric guitar through a speaker is the way you experience it naturally (unlike, say, an acoustic guitar or flute, which doesn't require an amp to produce its core sound). And that's still the best method, and the way big-budget rock albums are produced.

Another approach is to take a signal out of the guitar's amp through the line-out jack in the back of the amp's control panel. This way, the sound gets processed by the amplifier circuitry and gets enough juice behind it to provide the interface with a strong signal. Usually, you can turn down the speaker's volume independently of the line-out jack's level, or even defeat the speaker sound entirely, similar to the way plugging in headphones works. The disadvantage to the line-out method is that you're not getting the effect of the speaker, which many tone snobs agree is integral to the electric guitar's sound.

The third way to capture a guitar sound is to introduce a device that not only brings the guitar signal up to snuff electronically but also simulates what happens to it on its journey through a guitar amp—including the much-sought-after speaker effect. A whole cottage industry has sprung up around boxes designed for recording guitars. The Line 6 POD creates great distortion sounds but also simulates different types of clean signals. Many of the POD's sounds are digitally modeled after famous amps (by Marshall, Fender, Mesa/Boogie, etc.). You can dial up any amp sound you like on the box, plus add other effects such as reverb, chorus, and delay.