Koch archlute

 

This post is about why I chose a particular historical model for my client and how I altered it to suit his needs. Along the way I found that there were some visual trickery in historical lute making. 

This is my model of a small Christoph Koch archlute. It has a fretted string length is 59 cm with diapasons of 119 cm. These measurements are considerably different from the original lute. I took the photo with it leaning against my studio wall surrounded by small tools and the soundboard for a small theorbo in order to emphasis its size. 

My client formerly had one of my Venere theorbos (C 47, KHM) with string lengths of 79cm and 150cm. The soundboard in the photo was constructed for such a theorbo. He enjoys playing in a small ensemble but was finding his theorbo too much of a chore. He decided that a small archlute would enable him to continue making music with friends without the stress of handling a larger instrument. 

I supported his decision and immediately pulled out my drawing of the small Koch archlute that is conserved in Musée de la musique, Paris (E.546). I was familiar with this lute having seen it while studying other instruments in the museum. I did buy the museum's technical drawing because I was immediately attracted to it and thought the plans would come in handy. The original instrument is configured with an eleven fret neck, a fretted string length of 61.8 centimeters and diapasons of 142.9 centimeters. The fingerboard, neck and extension are all elaborately decorated. You can see the original lute here. The page also includes a short video of the lute's restoration and several audio videos of artists playing the restored lute. My client would not have wanted a long fretted neck and he did want a short extension. I thought the contours of the bowl and the shape of the soundboard would offer superior tone and volume even if I built it with a ten fret neck and a 119 centimeter extension.

 

The soundboard is only 405mm long but the face contour is full with a squat bottom.  The rose is located at 3/5 of the length of the belly and the open area of the rose is 1/3 of the belly width at the rose position. The bridge is set low on the belly and it spans 2/3 of its width at that position. The remaining area that hosts the J-bar and two short low diagonals appears cramped. This is the most important area for producing and controlling the sound of the lute. But the squatness of the form increases the area more than it would if the profile were more round. 

The contours of the bowl are important as well because they determine the internal air capacity.

Its depth is slightly more than half its width. (152mm vs. 300mm). But the significant increase in volume comes about from the high shoulders and squarish sides as seen in this view of the bowl's cross-section.

The side profile is full, flowing gently from its highest point and then dropping quickly to the neck joint. 

All of these features maximize the internal air volume of the bowl.

 

I approached building the mold with some trepidation because of my experience in building the Koch theorbo, No. 3581 Musikinstrumenten Museum of Berlin's Staatliches Institut für Musikforschung. See my post Theorbo after Christroph Koch, September 20, 2013. On that occasion I built the mold and it was only when I started making templates of the ribs that I discovered that the rib orientation was hopelessly out of alignment. I abandoned that mold and built a new one with the ribs aligned more uniformly.

 Before I started building the mold for this archlute I checked the accuracy of the rib alignment as described in the technical drawing. I made poster board templates of the cross-sections of the bowl and compared the ribs positions on the treble and bass sides. It was clear that the layout of the ribs was badly out of alignment on this lute too!

I thought it was strange that an experienced lute maker who built both an elaborately decorated theorbo and an archlute in expensive, exotic woods would be so clumsy as to construct a bowl with misaligned ribs. It was only when I started writing this post that I realized that rib alignment might have been a secondary consideration. I thought back to when I examined  a baroque lute built by Thomas Edlinger (NMM 10214 in Vermillion SD). The bowl is composed of 21 shaded yew ribs of varying widths.  However, the distribution of heart wood and sap wood is fairly even. It then became evident to me that the bowl was assembled to display the shaded yew as uniformly as possible with the wood that was on hand.  You can see the lute by following the links here. Both of the aforementioned Koch lutes have 15 ribs of flat sawn Kingwood, sometimes called violetta (Dalbergia cearensis). The ribs of both lutes display intense color and interesting grain patterns and the rib alignments on both lutes are asymmetrical. However, they show their wood grain to great advantage. My Koch bowl is Indian Rosewood cut from commercially available guitar sides. The holly spacers are 3 mm wide. I  also used this width of holly with the neck and extension veneers.

 

I proceeded to built an open pinewood mold with a central axis and five cross-sections per the plan but I  divided each cross section into 13 equal widths (the edge ribs are wider) and marked the position of each  rib. The rear of the mold is constructed with a wrap around form that is a little higher than what the end clasp will be. It provides support when the ribs are scraped clean and level. The wrap around is less than an inch thick so it provides a convenient surface for holding multiple small clamps when the gluing the end clasp.

 

 

 

 

Although I "corrected" the mold for rib width uniformity I did not alter the symmetry of the bowl's contours. That affected the position of the ribs as they wrapped around the tail end of the bowl. However, this irregularity is covered by the end clasp. See the earlier photo.

 

For all of the trouble the bowl caused me I was happy with the way it turned out.

 

 

I copied the positions and size of the rose but I used a different pattern than the original. The bridge position is the same too. the original lute has a long soundboard tongue that projects nearly two frets length over the neck joint. It does not look out of place and structurally it provides a little extra support to the bowl/neck joint.

 

Unfortunately, I did not photograph the barring that I used but if you watch the restoration video you will have a brief glimpse of it as the camera pans by. 

The top has a full set of harmonic bars; three between the bridge and the rose, three above the rose, three full width bars across the rose itself, two fingers on the treble side and a long J-bar that extends halfway under the finger bars.

 

I had doubts about the dense barring of the top but it is only 1.3 mm thick in the area from the rose to the bridge and 1.2 mm behind the bridge. Listening to the audio videos convinced me and I copied the thickness of the top and the barring scheme of the original archlute as closely as possible.

 

  

 

My extension is much different. It is much shorter by 23 centimeters, it has a different style of head, one that folds back on itself like the majority of Italian achhlutes. The lute can be strung in courses as a 13 course (1x1, 6x2, 6x1) or single strung as a 14 string (7x1, 7x1).

The original lute is 1x1, 5x1,8x1). I made this alteration at the request of my client.

 

 

 

The core wood of the extension is quartered spruce veneered with Indian rosewood cut from guitar sides and thinned to 1 mm. The back of the extension is flat like the original lute rather than contoured. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 For the extension head I use the design found on the Tieffenbrucker archlute  C.45, KHM.  

 

 

 

 

The neck core is quartered spruce veneered with Indian rosewood cut from a leftover guitar side and thinned to 1mm. A spacer of holly borders the rosewood followed by a strip of ebony. Even though I shortened the string length from 61.8 to 59 centimeters the neck was still long enough to carry ten tied frets. The tenth is held in place with the help of a small wood pin inserted into the middle rib with the fret looped over it.

 

 

 

 

 

 

 

I delivered the instrument strung in New Nylgut, carbon fibre and Savarez wound copper.

 

                                                          All photos by the author