Slide is the technique of using a glass bottle or piece of metal piping on the guitar strings to, no surprise, slide into, out of, and in between notes. A slide acts like a nut or piece of fret wire, creating a new endpoint from which the strings rest and ring.
Because a slide is not actually used to press strings down to the fretboard, but instead glides along top of the strings, it’s possible to play microtones, which are notes that fall between the semitones (between the frets). For this reason, slide guitar is very expressive and has a vocal‐like quality.
For quick reference, listen to Lynyrd Skynyrd’s “Free Bird,” which may be the most recognizable modern slide guitar recording.
Choosing a slide
There are different materials used to make slides, and each material produces a slightly different sound. Materials include glass, brass, stainless steel, chrome, copper, porcelain, and Pyrex. Generally speaking, the more mass (thickness) a slide has, the greater the volume and sustain it produces. Hardness increases the high‐end frequencies. Thicker slides work better on acoustic guitars. Because electric guitars are aided by amplification, they can get away with thinner slides.
Deciding which finger to wear the slide on
Of equal importance to a slide’s sound is its feel and comfort of use. Slides are hollow and worn over a finger on your fretting hand. Slides are worn on the second, third, or fourth finger. Some players like to wear the slide on the fourth finger so that the other three fingers are free to fret normal notes and chords as needed.
Other players lack the necessary control to properly play slide guitar when the fourth finger is in use, so they opt for using the second or third finger instead. How tight a slide fits around your finger affects the control you have over it.
Explore your options and choose a finger that allows you to use the slide to the best of your abilities. Johnny Winter and Tom Petty’s Mike Campbell prefer to use their fourth fingers to play slide. Duane Allman used his third finger. Joe Walsh, Bonnie Raitt, and ZZ Top’s Billy Gibbons all wear their slides on their second fingers.What matters most is how well you use the slide. Whether you get use out of your other fingers is of secondary importance.
Using a slide properly
After you have a slide in hand and you’ve chosen a finger on which to wear it, the next steps are positioning it properly on the guitar strings and damping unwanted noise. Good slide technique requires you to:
Position the slide perpendicular to the strings, in the same direction as the frets.
Target notes by placing the slide directly over the fret wire, not in the spaces between the frets.
Push down with enough pressure so that the strings make full contact with the slide, but not so much pressure that the strings contact the frets. You don’t want the strings to rattle against the slide or against the frets.
Hold the slide level and apply equal pressure across all strings (or at least across the strings on which you’re targeting notes).
Use a finger or fingers behind the slide to dampen strings, much like you do when performing a bend.
Whether to pluck strings using a flatpick or using your fingers while playing slide is a matter of preference. Joe Walsh uses a pick, Duane Allman used bare fingers, George Harrison palmed his pick while using a slide, Bonnie Raitt plays finger-style using thumb and finger picks. Whatever you choose to do, just be sure to let target strings ring freely and prevent idle strings from making unwanted noise.
Like any type of guitar playing, producing a clean slide sound is a balancing act between your two hands, with various parts of your hands and fingers contributing to damping.
With normal guitar playing, the height of the strings over the fretboard (called the action) is set low. Low action makes it easier to fret notes, and prevents depressed strings from going sharp by being pulled too far out of alignment. With slide guitar playing however, low action can cause unwanted buzzing and rattling noise.
For this reason, many slide players adjust their guitars (called setup) with higher action in order to get the cleanest sound possible. Because slides aren’t used to press strings down to the fretboard, there’s no risk of pulling the strings sharp. In fact, instruments that are used strictly for slide playing — like dobros, resonator guitars, and in some cases, regular guitars — use a special attachment called an extension nut, which raises the strings extra high over the fretboard. Extension nuts work well for slide, but they make fretting with your fingers impossible.
