This is the extension of a Railich theorbo that I built last year. I chose these photos because the white edging makes the extension shows up well. It is veneered front and back with ebony and on the sides or 'cheeks' with walnut. It is long -- it measures 840mm between the fingerboard nut and the nut on the theorbo head.
At the joint to the neck the extension is 78m wide tapering to 30mm at the head end.
The thickness under the fingerboard nut is 22mm tapering to 18mm at the end. The theorbo head itself is another 30mm high without the nut. The top or face of the extension is flat while the back is arched from side to side. The cheeks are angled in from bottom to top.
All of this work removes wood which reduces weight. It also promotes an elegant appearance. You can see the pronounced curvature on the back of this Railich theorbo extension (MIM Brussels). This extension is unveneered solid wood that is stained/painted black.
Below are several photos of historical theorbo extensions. One is traditionally elegant while the other has its own beauty.
Matteo Sellas 1640, Musee de la musique, Paris. The curvature across the extension and the subtle slope in the line of the cheek is a style that I try to emulate. The weight of the ebony and ivory inlay is burdensome to the player. I can't image playing through a long rehearsal with this lute.
The photo on the right is of the Sebastian Schelle 1728,
The stain on necks such as these appear to have some 'body' or substance to them. I have the feeling that the finish is a mixture of pigment, oil and a little resin. The theorbo head of the same instrument, which is a later addition, has a completely different look (below) that is probably pigment with just a little oil.
I use different styles of theorbo extensions depending on the model of theorbo. German theorbos have a distinctive style and I make a close copy for those. Italian theorbos have a style that changes only in the details and I have developed several models. You can see the difference in the treatment in the area of the extension joint between the German and Italian instruments in two of the previous photos.
The extension for the Kaiser is a typical Italian design. I always use a core wood of yellow poplar either painted or veneered. For this client I veneered all sides with black dyed pear. The theorbo head is poplar as well, stained black. Other times I cut my own veneer using ebony, walnut or, like on my Tecchler archlute, bloodwood. I start by preparing a poplar wood blank cut a little oversize in length and width but tapered to the correct thickness -- allowing for the veneer. I layout the peg holes and drill them. Then I prepare the veneer for the top surface and glue that on. Since the surface is flat there is no special setup. Then I rout out the cavity for the strings using a template and a small router (laminate trimer) with a flush mounted bearing.
The template is screwed in place. One screw hole will disappear under the neck joint and the other, upper left, is screwed into a scrap of wood temporarily glued to the side of the extension. I can clean up the cavity and cut the distinctive characteristics now or wait until I finish the head. Below are two photos; the Railich pegbox to the left and then the Schelle.
These two photos bring to mind a consideration that I haven't mentioned. Clearly one theorbo is single strung throughout while the other is strung in courses on the fingerboard with single diapasons. There are few surviving single strung theorbos. Most of the theorbos that are built today are of models that survive with double strung fingerboard courses and single diapasons. Few modern theorboists, however, want this arrangement and ask for single strung instruments regardless of the model. The Kaiser theorbo is double strung on 'board', as I say, with single diapasons, but I build it with single strings.
All photographs by the author.
Next time I'll shape the rear of the extension, glue on the veneer, make the head, figure out the alignment of the extension, cut the joint and finally glue it together.