Slide guitar has a kind of magic about it. There's a harmonic richness inherent in that interaction between the string and the slide - be it made of glass or metal — that speaks to the soul. The plaintive wail of Duane Allman, the wild screaming blues of Dave Hole, the sweet melodies of George Harrison, the virtuosity of Derek Trucks — they all took this one playing style and used it to emphasise their personal uniqueness while also adding to the vocabulary of slide guitar that we all borrow from now.
If you wish to join them in the ranks of slide guitar aficionados, it takes a lot of blood, sweat and tears - as well as a little ingenuity. Most guitars don't arrive ready for slide straight out of the box, and some guitars just aren't good for slide at all no matter what you do with 'em. Here are the two most important things to consider when setting your guitar up for slide:
Raise The Action
This might seem like a no-brainer to those of us who have been playing slide for a while, but if there are any beginners reading this, then this simple piece of advice will make all the difference in the world. Nothing can discourage a beginning guitarist more than bad-sounding equipment that gets in the way of making music, and if you've ever attempted to play slide on a guitar with low strings, you'll be aware of the clattering, clanging, clunking sound of slide against fret. The whole point of slide guitar is to remove the frets from the equation completely, in order to have a more direct line to the microtonal capabilities of the string: the notes in between the frets. And if your strings are too low, you'll be accidentally hitting those frets an awful lot - and making an awful noise. So the first thing you'll need to do when setting a guitar up for slide is to raise the action to a level that keeps you well away from the frets. But it's usually not enough to raise the strings at the bridge end: for true slide bliss it helps to install a tall nut as well, raising the strings up at the low end of the fretboard as well as the high. This is work for a qualified tech unless you're comfortable doing it yourself (and having a tech on speed-dial in case something goes wrong) but there's an easier way: commercially-available slide guitar extension nuts are inexpensive and non-destructive, simply slipping over the guitar's existing nut and raising the strings nice and high above the frets. This means you can dig in with the slide with complete confidence no matter where you are on the neck, knowing that you won't be adding a whole bunch of noises that you don't want.
As for string gauge, slide tends to work best with medium to heavy gauge strings: they're louder than light strings, for starters. Also, a lot of non-slide players use light strings as a compromise that makes fretting a little easier on the fingertips — sometimes at the expense of a little bit of tone — and this is simply not a concern when you're not fretting!
Don't Go Nuts With High Output Pickups
Slide guitar is so powerful, so expressive and so emotive, and to get the most out of the technique it really helps to use pickups skewed toward vintage output levels rather than modern higher gain pickups. Many great slide tones were captured with Gibson PAF hum buckers and there are all sorts of current models that capture different takes on that tone. The '57 Classic is especially slide-friendly, as are all three of the Burstbuckers, especially the Burstbucker 1, while P-90 single coils will give you an edgier, raunchier, dirtier tone compared to the sweetness of a vintage-voiced humbucker. There are no hard and fast rules with regard to pickup height on a guitar with slide: as with any guitar, it just comes down to what sounds good, and what doesn’t interfere with the free vibration of the strings. If the pickups are too high, they’ll interrupt sustain and could even create ‘wolf tones’ - weird “Did you hear that?” oscillating overtones that can make it sound like you’re out of tune. If they’re too low, your sound could become thin and noisy. And a set of super-heavy strings will sound different through the same pickup compared to a set of medium-gauge strings on the very same guitar. And depending on how hard you pick, your pickups will respond differently at different heights. And that’s part of what’s so great about slide guitar in general: by forcing you to more intimately interact with the string itself, it brings you that little bit closer to a direct line between your heart and the listener’s ears.
For a particularly slide-friendly Gibson, check out the Gibson Custom Dickey Betts SG or, for a particularly wide range of tones, the Epiphone Nighthawk Custom Reissue.