Here are some basic instructions to make an instrument first seen in the 15th century. The original fingering may well have been very different but the suggestion here complies with a modern recorder which will make it easier for most people to play.
Materials one hollowed cows horn-complete (smaller horns are better unless you have very large lungs !) one block of wood I used pine but something like cedar or other hardwood may be better. 10mm-20mm thick Equipment Drill Various drill bits sharp knife or scalpel saw. Electronic tuner(optional) Method 1. Clean horn 2. Measure a block of wood to fit the open/big end of the horn, carefully sand this down until it very nearly fits. (It should be slightly tapered) Cut a windway in square section(approx 1cm across) into the depth of the block, then end that is furthest into the horn should be sanded to a 45 degree angle not a sharp 90 degree edge. 3. Boil some water with the large end of the horn in it until the horn seems to soften, forcefully push the block into the end to make a good seal. 4. Let dry throughly. 5. Cut the rectangular window (mine is 10mm)so the top is just level with the end of the block, then cut the slope from the narrow end of the horn to the exit, this adjusts the quality of your sound so do it bit by bit until the sound is as you like it. 6. Drill holes starting about 25mm from the window and a intervals of 18mm. I did six on the front , but 7 plus one on the back may be better if you play a recorder ! Start small 3-4mm ,you enlarge them to tune the instrument, very carefully with the scalpel, I'm told by ear no more than 15 mins at a time, I can't tune except with a electronic tuner. Your Gemshorn is ready to play !
Note: Measurements are for a horn approx 300mm length, adjust as necessary for bigger horns.
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Fingering-the Modern way A gemshorn is just a big ocarina really. You could put four holes on the front and one on the back and tune them to work with ocarina fingering, . But most people would prefer a thumbhole and 7 finger holes with recorder fingering as follows (imagining the instrument to be in C): C 0 123 4567 d 0 123 456- e 0 123 45-- f 0 123 4-67 or 0 123 4-6- g 0 123 ---- a 0 12- ---- b 0 1-- ----- c 0 -2- ---- d' - -2- ---- Anything else is a bonus!
Plaster Block(a suggestion from a friend down under) Making gemshorns is a lot of fun. "Down under" here in Perth, we get enormous horns from wild cattle in the Kimberley Region of Northern Western Australia. Wood can be used for blocks, but another quicker and easier way to make blocks for gemshorns is to use plaster of Paris. Take a shallow tin (eg, one of those little tins those little camembert cheeses comes in) and drill a hole through the bottom wide enough to take a carriage bolt. Pass the bolt through the bottom of the tin so that the screw end is inside the tin. Fasten a nut around the end of the bolt so that it is flush with the tip of the bolt and flat against the floor of the tin. Fix the bolt in place with plasticene on the underside of the tin. Place this contraption on top of something firm so that the bolt can hang down without being forced up through the tin. I use a sort of miniature workbench called a "Workmate" which is little more than a giant clamp with wooden jaws. Clean up the horn and cut it to size. Fashion the cut up (window/labium) with a sharp chisel. Lightly grease the inside and outside of the horn with Vaseline (to the depth of the little tin). Now, fill the tin with freshly mixed plaster of Paris. Up-end the horn in the centre of the tin and secure it somehow so that it doesn't fall over. Let the plaster harden overnight. When it is dry undo the bolt carefully and withdraw it from the tin. Remove the horn (and hardened plaster) from the tin. Carefully chip away the excess plaster from around the horn if necessary. Replace the bolt in the nut which is embedded in the face of the block. Pull on the bolt and the block will slide out. It shouldn't need too much encouragement. Now you can proceed as you would with a wooden block, though plaster of Paris is a bit tricky to work. Again, a nice sharp chisel does the trick. If you make a mistake it is easy enough to cast another block. As you test your voicing the bolt and nut arrangement
makes it very easy to withdraw the block. One problem with gemshorns is that the horn changes its dimensions considerably with changes in humidity. I imagine a wooden block could easily be pushed out of the horn when the latter contracts. I find that it helps to keep the instrument in a plastic bag in which one has sprinkled some water. I also find it helps to steam the horn over a saucepan of boiling water before inserting the block. Paraffin wax can be used to improve the seal of the block if this becomes a problem. The external face of the block should be coated with a suitable plastic varnish. Alternatively, you can glue to it a piece of polished leather cut to size.
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