A common misconception about the solid body electric guitar is that its sound is derived solely from its magnetic pickups transmitting the vibrations of the strings. In fact, a Stratocaster, Telecaster, Les Paul, or any of their boutique emulations, resonates in an acoustic fashion that not only influences the sound captured by the magnetic pickups, but also goes into the air in much the same way as an acoustic guitar, if more quietly. In fact, Buddy Holly’s producer Norman Petty used to mic the strings of Holly’s Strat, in addition to miking his amp, in order to add an acoustic attack to the mix. Having established that it's not just the magnetic pickups generating sound on a solid body, we can open up a world of tones with a contact microphone.
A contact microphone senses audio vibrations through contact with objects. Unlike a dynamic Shure SM57 or a ribbon type Royer R-10 microphone, contact microphones are largely (but not completely) insensitive to air vibrations. They almost entirely transduce sound from the material they're in contact with.
An early adopter of the contact mic as an experimental tools was the innovative guitarist Fred Frith. “I started out with a mic removed from a telephone taped to an acoustic guitar headstock,” he says. He now has a magnetic pick-up bolted onto the nut, but has used contact mics in addition “to explore percussive elements.”
Norwegian guitarist Eivind Aarset installed a contact mic where the neck of his instrument meets the body. A toggle switch lets him use it alone or in conjunction with the magnetic pickups. By itself, it gives his guitar a banjo quality. He also employs it when bowing the guitar and for making various noises.
One of the reasons Nels Cline and others like the Fender Jazzmaster is that they can pick behind the bridge for a Gamelan or ring modulator-style tone. The effect of that sound is greatly multiplied if you have a contact mic attached to the tailpiece under the strings.
If you think you would like to experiment with a contact mic on a solid body instrument, it is extremely easy. Contact mics are incredibly cheap: you can get a Neewer 5-Pack for $15 on Amazon. They come with female ¼" jack ends, so plugging in is simple. Before you do so, however, I recommend you place a volume pedal or mute-able tuner pedal between the mic and your amp so you can quickly kill the signal – when the mic is not in contact with your guitar it may feed back.
Once you’re set up, pretend you’re a doctor with a stethoscope and place the mic in various positions on the body, neck, tailpiece, headstock, etc. These types of mics often come with sticky tape embedded, but if you don’t want glue all over your guitar, leave the protective coating on the tape and just hold the mic in place as you strum the open strings. You should be able to get a clear idea of the sound produced by that spot. Once you know where you want it, you can decide if you want to stick it on, or have one imbedded in that area or in multiple areas.
An electric guitar with two or three magnetic pickups is already a versatile tone machine. If you add one or more contact mics and a few effects, you can increase the sonic possibilities geometrically, if not exponentially.