I’ve never met an acoustic guitar that didn’t deserve a good spanking. In the hunt for exciting new sounds, you may find that even the most delicate looking, ornately crafted steel-string just needs to get slapped—hard. Why? Well, as one quick listen to the full-contact guitar playing of Preston Reed, Monte Montgomery, Kaki King, or the late, great Michael Hedges will show you, slapping a steel-string not only adds a thrilling percussive element to your riffs, it also allows you to send bright harmonics flying forth from your guitar with each strike of your hand, like sparks shooting off a blacksmith’s anvil.
Just as it’s best to learn to walk before you try to run, it’s advisable to learn how to tap before you slap. For instance, the ordinary harmonics in Ex. 1 are not plucked, but struck—they’re tapped using six quick strikes of the picking hand’s index (or middle) finger exactly over the 12th fret. In the tablature staff, each tapped harmonic is represented by two numbers: its fretted position (in this case “0”) and its diamond- enclosed tapped position, which, in the case of an octave harmonic, will be exactly 12 frets higher. To make a harmonic really chime, your tapping finger should be slightly limber so that when your wrist propels it into the fretboard, it bounces off the string immediately after the string collides with the fret, like a piano hammer bouncing off piano wire.
Now, go for a much bigger sound by slapping four 12th-fret harmonics simultaneously using your fully extended index or middle finger (or some combination of the two) as suggested by the harmonic clusters in Ex. 2. Or take a more “funk bass” approach and smack the strings with the side of your thumb. Remember to also try the 7th and 5th positions, as shown—they’ll yield harmonics an octave-and-a-fifth or two octaves higher in pitch, respectively.
The real fun with octave harmonics begins once you realize you can achieve them not just by striking exactly 12 frets above the nut, but also by striking the same distance above fretted notes. For instance, in Ex. 3, an E harmonic is sounded by fretting E at the 2nd fret of the fourth string, and slapping the same string exactly an octave higher at the 14th fret. By tracing entire chords in this manner, you can get heavenly ascending textures such as Ex. 4’s rising Fmaj7 arpeggio. Here, we simply trace the diagonally shaped chord one tone at a time exactly 12 frets higher up the neck, letting each note bleed into the next. To get all four harmonics in Fmaj7 to ring with a single strike, hit all four strings at once, just as we did in Ex. 2, but this time, slap at a diagonal, precisely mimicking Fmaj7’s shape an octave up the neck [Ex. 5]. Also, as acoustic-electric powerhouse Monte Montgomery will tell you, if your guitar is rigged with a pickup and you’re amplified, a heavy dose of compression will really make harmonics—and, if you’re not careful, your entire guitar—scream wildly.
This near-abusive spanking tactic works wonderfully on chord progressions like Ex 6. To get the harmonics in the first bar of this phrase to ring, again, try to replicate the chord shapes. Strike the high notes in F/G at a near 45-degree angle, and the high notes in C/G at a slightly more vertical slant, followed by a perfectly vertical G triad struck at the 12th fret—all the while interspersing slapped G bass harmonics at the 15th fret of the lowest string. Though the thumb may not be capable of slapping as many strings as a finger, it has a wider range of motion and can more easily adapt to shifting shapes—perhaps making it the sensible choice for this lick.
Remember, slapping harmonics is not an exact science, and it’s often nearly impossible to get every note in a riff to sound as in glorious partials. Ex. 7, for instance, is a chunky slapped phrase that features three big chords that have an “open E chord” shape that’s hard to mimic with a slapped picking-hand finger. The lick also calls for the open first and second strings to be slapped, but not necessarily played as harmonics. Luckily, a little sparkle goes a long way, and the beauty of harmonics is that even if only one or two of them ring within a chord, by simple psycho-acoustic association your listeners will likely believe they’re hearing many more.
Finally, don’t forget that slapping is the essence of funk bass, and acoustic guitarists can achieve similarly groovy, butt-shakin’ slapped riffs on their dreadnoughts. Guitarists can also alternate between a bass line and slapped harmonic clusters, as proves the F#m7 and B7 chords in the highly staccato Ex. 8. Slap with your thumb throughout this lick and remember: When you prize attitude, vibe, and grit over accuracy, the only one who will feel the impact of your slapped riffs more than your guitar is your listener.