Action and Intonation

The topic of proper height of the strings above the frets (the action) and correct placement of frets with respect to the nut and bridge (intonation) will embroil a group of luthiers in debate as few other topics will. These two topics touch on the heart of the physical basis of musical tone generation, a matter which is mysteriously entwined between the laws of physics and the physiology of perception. Even a cursory treatment of the topic is beyond the scope of this discussion, and one upon which I would embark with extreme caution in any case.

With that as a preamble, here are several basic observations which might be useful to anyone as a practical guide to evaluating a musical instrument's general playability:

Action
A dulcimer's ease of playing rests critically on the height of the strings above the frets or its "action." Basically, one wants the strings high enough so no string will buzz on any fret. Beyond that criterion, tastes vary. Some people like a firm feel when they fret--a little "push-back" feeling from the strings. Such an action can be achieved by using heavier gauge strings or by raising the height of the strings. The height can be raised by changing the height of the nut or the saddle, but the nut is usually the element that is adjusted, as the saddle is far from any of the frets and so would require much more of a difference in height to change the action.

Other players like a lighter action so the hand can glide from one complex chord to the next with a minimum of effort. Such an effect can be achieved, of course, by the opposite maneuver: lowering the height of the strings or equipping with lighter gauge strings.

When string gauge is changed to vary the action, the instrument's voicing is varied, too. Here we step gingerly into the first hint of a topic which can become a pounding surf. For those who want to go further, you can use the internet's deja news search engine to look for articles dealing with "string gauge," "intonation," "compensation," etc. Prepare for a deluge! Broadly and somewhat simply speaking, we can say that lighter gauge strings give a sweeter though quieter voice, while heavier gauges give the instrument a more open sound and louder volume.

Generally, the action at the nut will be just a little higher than the height of the first fret, so there is no buzzing there. Then the height of the saddle is set just a little higher than necessary to avoid any buzzing on the rest of the frets. If the fretboard has been carefully made, that is all there is to action.

You might sometimes find a slight flat area on the tops of some frets. This indicates that the luthier has "joined" the frets to make them more accurately flat with respect to the strings. Joining is the process of leveling the frets with a file, then using a special file called a crowning file to reshape the top of each fret to eliminate the flattened area. This keeps the instrument more accurately in tune and eliminates tiny buzzes that can happen when a string is fretted and buzzes against the fret's flat top. A joined fretboard can also (but not always) indicate that the maker has put the action as low as possible, dressing each fret individually to exactly the same height in order to eliminate buzzing rather than simply raising the action.

Action which is too high can cause an otherwise nicely made instrument to be unplayable, for two reasons. First, it takes more effort to press down the strings. Secondly, the more you have to press the string down, the more you increase the tension. That increase in tension can sharp the note to a surprising degree. The higher the action, the more pronounced the sharping. This is an effect of fretting no matter how low the action is, and the process of compensating for it is called "intonation," our next topic.

Intonation
Intonation is a second thorny topic. The matter of compensating for the sharping effect of fretting a string is called "intonating." When a fretted stringed instrument will play accurately at all frets on all strings, it is "compensated." Briefly put, compensation is achieved by moving the saddle (bridge) further from the nut so the effective length of the string is a little longer, "flatting" the string to compensate for the sharping effect incurred in fretting. (Sometimes it is also advisable to move the nut also under one or more strings, but is not a general practice in dulcimer making.)

The controversy, of course, comes in agreeing on a method for judging how much to move the saddle. And once that controversy is joined, someone inevitably points out the futile nature of such arguments since hardly anyone actually knows how to accurately tune a stringed instrument anyway. After several volleys and broadsides in this battle, someone else further observes the uselessness of that fracas by observing that Equal Temperament is a farce in the first place, and we should all be playing with Just Intonation except that Western Culture was perverted by the Baroque movement, or some such provocation.

The discussion then degenerates into a dog fight and re-emerges a couple months later into civil discourse, with profound apologies for ill-advised and rash statements all around and philosophical anguish about how we should all try to "just get along."

Let me offer a modest practical demonstration of how I set the action and intonation of the Appalachian dulcimers I make at Bear Meadow. That will give you a specific idea of how one person does it and also afford a context in which to begin examining the more arcane corners of the art, if you are inclined to do so.

A practical method for setting the action and intonation in the fretted dulcimer
Setting the action: In order to properly intonate the instrument, it must have the action set first.

I normally set the nut height to .015" higher than the fret crown. For instance, I usually use a .032" crown fret, so I set the nut to hold the strings .047" above the fretboard. To set the saddle end of the action, I do the following before placing the saddle permanently on the instrument:

1. Equip instrument with its highest and lowest strings.
2. Place a temporary bridge approximately where the bridge is to go. I make a small bone piece shaped like a wedge so that by sliding the bone further under the string, its height increases.
3. Tune the bass string a whole step lower than the usual tuning. If you ordinarily tune to aAA, then tune to G. This will give the string every chance to buzz.
4. With the temporary bridge in place, play a scale all the way up the bass string, noting where any buzzes occur.
5. If there is only one place the buzz happens, inspect the next highest fret. It may be too high. If it has come up out of its slot, try knocking it gently back with a light-weight hammer. While doing this tapping, grasp the dulcimer by the edges of the fretboard and hold it a half-inch or so above the table, so the instrument doesn't absorb the full shock of the hammer taps. If this doesn't work, consider joining the fret (see above).
6. After eliminating any single buzzing frets, withdraw the temporary bridge slightly, which will minutely lower the height of the bass string. Run the scale again. If there are no buzzes, lower the string and repeat until the string begins to buzz against one or more strings. If it buzzes against only one, go back to step 5. If it buzzes against a group of frets, you have found the lower limit of the bass string's height.
7. Increase the string's height by moving the wedge-shaped temporary bridge further under the string, until there is no more buzzing.
8. Now check for back buzzes. Fret the bass string IN FRONT of the fret rather than behind it, and pluck the string between the fret and the nut. Any buzzing on the frets is a back buzz and indicates the nut is too low. Repeat the test for the first six frets. If you find back buzzes, raise the nut .005" and try again.
9. When you have eliminated all buzzes on the bass string, mark the position of the string on the wedge of your temporary bridge. This is the saddle height.

When you have successfully completed this procedure, make a small bone square as high as your measured string length, as wide as your final saddle, and as long as the fretboard. File the edges off the top, side, front, and back. This gives you a nice inverted V edge which will accurately define the string length. Or if you are musician following this because you want to put your floating bridge back in its right place, use your floating bridge in all that follows. Mount your temporary saddle on the fretboard about where it should go (don't be too fussy now, as long as you get it about right within an inch). Tune both strings up to concert pitch, an octave apart. Use a tuner to get the pitch right, then turn the tuner off. The rest your ear will be better at than the tuner. You are ready to intonate your dulcimer.

Refine the tuning of your two strings so that they are exactly an octave apart.
1. Rely on your ears' ability to hear beat tones, not on your electronic tuner. It will help to turn off the radio, the air conditioner, furnace blower, etc. If traffic noise outside is loud, choose a quieter time. Absolute quiet is required for this process. Strike the first harmonic of the bass string and listen for beats against the first string. They must be in absolute unison.

2. Now fret the bass string at the 7th fret and shortly thereafter pluck the first string. These two should also be in unison. If the bass string is flat, slide the temporary saddle toward the nut, shortening the string. If the bass is sharp, slide the saddle away. Now go back to step 1 and re-tune so that both strings are in unison. When you get a unison in both step 1 and 2, your bass string is now compensated. The next thing is to compensate the first string.

3. Re-check that your bass and first string are still in unison. Then fret the first string at the 7th fret, then strike the bass string's second harmonic (approximately above the 3rd fret). The two tones should be in unison.

4. If the first string is sharp, carefully move the temporary saddle further away WITHOUT disturbing its position under the bass string. Similarly, if the first string is flat, move the saddle closer. Now go back to step 3. When you get a unison in both steps 3 and 4, go back to step 1 and re-check. When you get a unison in all 4 steps, go to step 5.

5. Now use a sharp knife to cut a line into the fretboard against the front and back edge of the saddle, defining its true position. Congratulate yourself for you have just intonated your musical instrument.

The next step would be to cut a groove in the fretboard at that place and fit a permanent saddle of the correct height into the bridge. Then the other two strings can be fitted to the dulcimer. There are further subtleties to be observed that many luthiers will find missing from this description. Nevertheless, it is complete as it stands, and is the basic procedure I use in most cases.

The floating bridge
Some makers do not fix the bridge in a slot on the fretboard, but leave it to be fixed by the pressure of the strings. This has several virtues, but an important failing: sooner or later a musician finds (or suspects) that the bridge has slipped from its correct position, and thereafter curses the luthier who made the instrument without indicating the proper position of the bridge.

You can use the method shown above to find the correct location of the bridge. Once you have it, you can score along each edge into the fretboard with a sharp knife, creating "witness lines."

But why didn't the luthier who made the dulcimer do that in the first place? Of course the maker could have fixed the bridge with a spot of glue or drawn witness lines. But the size of strings you use and the tunings you choose will have minute influence on the intonation of your instrument. You can take advantage of the lack of pre-defined compensation to set your dulcimer's compensation as accurately as you wish. Of course, that is making the best of a bad situation. You are entitled, as a player of a fretted instrument, to a compensated axe. You really shouldn't have to be a luthier to set it up!

The zero fret
Some dulcimers are equipped with a fret behind the first fret, where the nut would ordinarily be found. This is the so-called "zero fret" and does the job of defining the tone of the open string. Behind the zero fret will be found a slotted piece of material which guides the strings toward their various tuners while preserving the spacing between strings on the fretboard.

I used to be very much against the zero fret, but now I'm just mildly grumpy about its use. I've found that in most instances, the zero fret's failings do not contribute to any failing of the instrument. Nevertheless, although I've stopped recommending against them, here are my reasons for not using them in Bear Meadow instruments:

1. The height of the nut can be readily adjusted for buzzing. This can be an important element in dealing with "winter blues" and compensating for small changes in the profile of the fretboard. The zero fret would have to be pulled and replaced by a higher fret (not a lot of choices about crown height in frets).

2. In some tunings, a compensated nut can be quite advantageous. The zero fret cannot be profiled to do any such thing as that.

3. The angle at which a string breaks behind the nut and the saddle is critical to the clarity of the tone. A string lying passively across a nut has no such sharp defining angle. It is not even an approximation of the break angle achieved when the string is fretted, since that action bends the string across the back of the fret, not simply pressing it against the fret's top. For that reason, a string stopped by a zero fret will not have all the clarity and crispness of a string stopped by a well-made and well-placed nut.

Dwain Wilder is a luthier in Rochester, New York. Do you have comments or questions about his article? Contact Mr. Wilder directly by e-mail. To learn more about him, see the Contributors section of Sweet Music Index.