Pitch, as a musical term, refers to the frequency at which a given object or air column naturally vibrates. This may be one clearly defined pitch, as with a flute, or it may be a jumble of many frequencies, as with a drum. Most instruments fall somewhere in between these two extremes. Free reeds are more like a drum than a flute. Pitch is directly related to mass, length, tension, material density and, in some cases, the intensity of the energy being put into the vibrating system. These (and other) factors do not appear equally in all instruments, depending on what manner of sound production is used by a particular instrument. Wind instruments use a vibrating air column whose dimensions can be altered; but the material density of the air is a constant (with small allowances for temperature and humidity). Strings can be altered in tension, mass and material density and are usually connected to a resonance chamber which, being filled with air, can display characteristics of a vibrating air column. You can see how subtle changes make a big difference in the sound of an instrument. This is why a clarinet sounds different than a saxophone, trumpets sound like trumpets and trombones like trombones, etc.
When we hear an instrument, we can identify the sound because we recognize the subtle elements that define that particular instrument. It does not matter so much which note is being played, (the pitch) we still know the instrument's individual sound. The physical characteristics of playing the instrument (blowing, plucking, striking, rubbing, etc.) are big audible hints and I will mostly overlook them or this will be a book before I get to tuning a trump (instead of just a novella). These playing techniques are of particular importance to trumpists defining not only the overall instrument, but the style which is played. Of more importance in this discussion is the sound quality and frequency of the vibrating system.
A flute is the closest to producing a pure note, free from strong harmonics (multiples of the lowest frequency). The drum lives at the other end of this spectrum, having so many harmonics that no lowest frequency is determinable as a specific pitch. Trumps share both of these characteristics. A wide array of pitches, based on a certain lowest frequency, are produced in the reed's drone. By matching the resonance chamber to a harmonic, a flutish tone is produced. These tones are very pure because they are segregated from the reed's harmonic series and cannot, therefore, have their own harmonics. The drone, of course, mitigates this purity and they combine to produce the tones of the trump. Mouth cavity instruments are unique in the ability to rapidly and accurately match various harmonics of the drone with a tuned resonance chamber.
Standard tuning has been established so that various instruments can play together and be in tune. Each note of the scale has an assigned frequency mathematically relative to this A note. Electronic tuners are modern man's gift to trump tuners, although even they can't be trusted, as I'll explain later.
In tuning a trump, the lowest frequency at which the reed is vibrating is used as the stated pitch of the instrument. The scale of harmonics available will most closely resemble the scale which uses the same note as its root. The reed's pitch is dependent upon the length, mass and stiffness. The reed's sound quality is dependent on pitch and many elements of the harp itself. The steel's molecular structure, temper and surface texture as well as edge shape, tolerance with frame, length of trigger in relation to reed, and a myriad of subtleties all come into play. A balance between all of these elements yields the best harps.
Altering the pitch of a reed has an effect on the other aspects of the instrument's playability. I have ruined harps in the tuning process after spending many hours constructing them. If you try to make a reed too low, it loses the stiffness needed to perform well in other aspects.
I have taken the long road in getting to the actual tuning to stress how each aspect of a harp's set up influences the others. Fine tuning of a harp should be kept to a minimum and go slowly.
So here is how it is done. To lower the pitch of a steel harp, the reed must either be made heavier or less stiff. Added mass is most effective furthest away from the crimp. Reducing stiffness is most effective near the crimp. Beeswax, solder, thread, lead and other adhesives can be added to the trigger to increase mass. These attachments must be securely fastened. The advantage here is you won't ruin the harp and can remove the attachment if it doesn't work. A bead of solder in the loop of the trigger and be partially removed to fine tune.
Lowering by removal is permanent; you can't put it back. Even if you used attachments to restore the pitch, the playability of the instrument will most likely have been altered. This may be a good thing if the instrument was too stiff anyway, or...be careful.
To lower the pitch by grinding or filing, remove small amounts of metal near the reed's base. Some makers grind the face of the reed and some the edges. It is very important that the removal is not abrupt, creating a stress point. This is especially true of face grinding. Work slowly, check your progress often. Feather your cuts out but concentration on area approximately 1/4" to 3/4" from the crimp. This is a very good way to lower a harp to its nearest standard pitch, but don't try to go too far.
Robbie Clement recently told me that an old way of lowering the pitch was to hammer the reed near the crimp, thus thinning the steel, making it less stiff. As of yet, I have not tried this.
To raise the pitch of the harp, material must be removed from the trigger. Face grinding the embouchure area of the reed also will work, but I don't recommend it. A small pitch increase can be had by grinding the sides of the trigger as long as it is not made too thin. If it is a long trigger, it can be shortened and a new loop bent. Always heat the tip when rolling a loop or the steel may break rather than bend. Keep the heat away from the reed proper to preserve its temper. Changing temper will change the pitch and is, to my limited understanding, an uncontrollable aspect of tuning and may significantly impact the playability.
Trumps are more easily lowered and the little bit that a harp can be brought back up may best be saved for the tuning when you go just a little too low.
Confused by Trumps
Electronic tuners are confused by trumps, and a bit unreliable. If the harp has good sustain, it can be plucked without a resonance chamber and very close to the tuners pick up. The tuner must have a meter to be of much use. What you are watching is the change of a few cents and just lights won't do. Also, and perhaps more importantly, you don't want your free plucked steel harp at pitch or it will play too sharp. Tune approximately 10 cents flat and they play more in tune. I suspect that the added mass of the jawbone is responsible for this, but don't really know. Opinions anyone?
If you play the harp into the tuner, the mouth's subtle shifts make a reproducible test difficult and the changes of only a few cents are blurred.
The best method for tuning may be to have a standard pitch played and train the ear to recognize when they are synchronous. After all, we don't perform to our tuners and who rally cares if the light comes on, as long as it sounds good. This is the time tested method.
Tuning bamboo trumps is much the same. Scraping the reed near its base lowers the pitch. Removing mass toward the playing area raises the pitch but is limited. DO NOT TUNE THIS 10 CENTS FLAT OR THEY WILL BE FLAT. This is why I think the jawbone affects the pitch of the steel harp which, unlike the bamboo, is in contact with the teeth.
Choose carefully those trumps which you tune. In the case of hand made harps, the makers may have had good reason to leave it where they did. Listen to the instrument, not just its voice, but also its spirit and it will tell you what it needs.
This site is best viewed in 800 x 600 x 64k colors or better