The diddley bow is played slide-style—that is, the pitch of the string
is changed by pressing a glass or metal object (a slide) against the string. When playing slide on a new
instrument, I rely on visual cues to get close to a note, and then on my ear to nail it. For advanced techniques,
such as harmonics, it is critical to have the positions marked. Therefore, I mark the note positions for
two octaves of a pentatonic scale (root, flat third, fourth, fifth, flat 7th, octave, etc.) on my instruments.
I use harmonics to find these positions, so let's spend a moment to talk about what harmonics are.
When the string on a diddley bow is struck, the
vibration of the string is complex, consisting of a fundamental (or, first harmonic, which is the loudest tone of the open
string) and several higher order harmonics (higher overtones). If you touch the exact mid-point of the
string very lightly with your finger and then strike the string with a stick, you should hear a chiming sound, one octave
higher than the sound of the open string. This tone is called the second harmonic, and you hear it
because you have damped the fundamental tone of the open string, allowing the harmonic to sound. If you
move your finger very slightly along the string, the chiming sound disappears. The place where the chiming
sound is the loudest is the midpoint of the string, and this is the place you mark on the board. Similarly,
if you touch the string a third of the way from the nut or bridge, you get a softer, but even higher-pitched, chiming sound.
This is the third harmonic, and you hear it because you have damped the fundamental and second harmonic.
Touching the string at a point one quarter of the way from the nut or bridge is the still softer fourth harmonic,
two octaves higher than the open string fundamental. You will need to strike the string fairly hard to
hear this one clearly, and with the type of wire we are using, this is about as many fundamentals as I can hear distinctly.
The harmonics get softer because the size (amplitude) of the vibration of each higher harmonic is smaller than the
lower ones or the fundamental. With this in mind, let's now find the locations for our position marks.
Step one: I find the center
of the string and make a big pencil mark at this position on the face of the instrument (the strongest harmonic is here).
On a guitar, this would be the equivalent of the 12 fret, one octave higher than the open string.
Step two, I next find the places where the string length was divided into thirds (there are strong harmonics here as well)
and mark these positions. On a guitar, these would be the equivalent of the 7th fret and the
19th fret, a fifth and an octave and a fifth higher than the open string, respectively.
Step three: I find the places where the string length was divided in fourths and mark these positions
(harmonics are achievable at these positions as well). On a guitar, these would be equivalent to the 5th
and 24th frets, a fourth and two octaves higher than the open string, respectively.
Step four: using a ruler or by eye, I mark the mid-point between the octave and the two octave positions
(five-eighths of the string length from the nut). This gives an octave and a fourth, equivalent to the
17th fret of a guitar. I use a slide to check this by ear.
five: using the slide, I find by ear and mark the positions equivalent to the 3rd, 10th, 15th
and 22nd frets. I mark these in pencil, because I find that, after playing a bit, I sometimes
need to adjust some of the marks. The position marks may be more visible if you use small pieces of blue
masking tape over the pencil marks.