Harpsichord - Fitting a singing buff

Harpsichord - Fitting a singing buff

This webpage gives advice to the amateur harpsichord maker or maintenance man on how to fit a "singing buff". This means a buff stop that will not produce the "pizzicato" effect: the high partials will be damped, but the whole string hardly so, modifying the sound yet allowing the vibrations to last for a few seconds, allowing for subtleties of articulation and successfully reproducing the sound of a lute or guitar.

1. STRING CHOIRS AND DOUBLE BUFFS. In an instrument with two 8' choirs, you may wish to fit a "singing buff" (notes with a slow decay whereby the sound will last many seconds) to one choir and a "damping buff" (notes with a fast decay whereby the sound will last for a few seconds only) to the other choir. Both alternatives will work with either choir, regardless of the instrument model. Incidentally, double buffs are historical, though rare. The author finds that the damping effect is more suitable for a front 8' choir, while the singing effect is more suitable for a back 8' choir, but this is subjective: feel free to experiment with one or two pads, and maybe make the opposite selection if you prefer so.

2. THE BUFF MATERIAL. Buff pads have been—and are—made of either cloth or leather. For a singing buff, cloth will not do: you need leather. For the large pads in the bass the leather should be at least 3-4mm (millimetres) thick, and the ideal material is buffalo—or similarly soft—hide. You will need thinner hide for the tenor. Finally, for the treble you need 1mm-thin pads, thus they should be slightly stronger: a soft piece of cow hide will do. Mind that the amount of material you need is minimal: for a large harpsichord with buff in both 8' choirs, all the pads put together would cover a surface not larger than 600mm2 (2 sq. in.).

3.THE BUFF BATTEN. In most harpsichords the batten is located against the nut. If yours is even a few millimetres away from the nut, there is no way you can fit a singing buff. The upper surface of the batten is normally about 1-2mm below the string. The batten should be at least 5mm wide.

4. THE PAD HEIGHT. The height of each pad—from its top to its bottom glued to the batten—is uniform, about 3mm, so that the string is touched by the middle of the pad.

5. THE PAD THICKNESS. By this here we mean the left-to-right distance once the pad is glued. This size is also uniform. If you are fitting a buff against one 8' string choir only, you can make the pads 6mm thick if you wish. If you are instead fitting separate pads to each 8' choir, allowing for the typical distances between strings and the space needed to move the batten so that both sets of pads clear the strings (by no less than 1mm), each pad will be about 4mm thick.

It is not important if the string is touched by the "uncut" hide surface or by any of the surfaces that you cut in the process: mind only to be consistent in this respect, in order to achieve a uniform effect.

6. THE PAD WIDTH. By this we mean the distance between the front and the back of each pad: this is the length of string that will be touched by the pad. It is the single most important element in defining whether you are going to have a "singing buff" or a "damping buff", and whether the effect will be uniform across the instrument's range. Many makers—past and present—would fit uniform pads of the same width: this may yield a buff that is "singing" in the bass, but will become "damping" in the tenor and even more so in the treble. This is why Hubbard in his instructions for his French harpsichord kit in 1970 (p. 63) recommended to have the pads decreasing in width and to ensure that all the notes are evenly buffed.

The table below shows the authors' recommended pad width in millimetres for both a "damping buff" and a "singing buff". These sizes have been derived empirically by experimentation, and relate to the frequencies of harmonics to be damped. They will work on any model of harpsichord, virginal or spinet. The table below covers all the historical ranges, and is meant as a guideline only: feel free to modify it if you previously experiment with pads and find that your instrument—or your personal taste—requires different widths.

7. GLUING THE PADS. Once you have cut and sorted the pads, fitting them to act evently on all the strings is very simple. Let us assume the buff batten has initially no pads. First put the batten in the position for the left pads to be ON, buffing the long string of each 8' pair. Place some block of wood somewhere to ensure that the batten does not move at all during the whole operation. Now take each pad, spread a thin coat of glue in its bottom (vinyl glue will do) and place the pad gently touching the string, the nearest border flush with the end of the buff batten, i.e. where the latter meets the nut. Repeat for all the strings. Wait until the glue is dry. Now move the batten 2mm to the right: 1 mm to clear the pads for the "buff off" position, and a further millimetre for the buff batten to be on again, but now acting on the short string of each pair. Repeat the pad gluing operation as before for the short 8' string choir. Once you have finished, the buff pads should look like in the picture below.

The double buff in the bass and treble of the Hubbard-Di Veroli harpsichord ( installed in 1974, photographed in 2011)

8. SOUND EXAMPLES IN YOUTUBE. Recorded on the Hubbard-Di Veroli harpsichord:

The Hubbard-Di Veroli harpsichord: with pins but not strings yet (1974) and completed (1975).