Stockhausen Slit Drum

On the heels of the Heaven's Door commission, Stuart has commissioned these instruments to perform Stockhausen's "Zyklus" and "Kontakte". I am building these out of the same quarter sawn sapele that was used for the Heaven's Door plates. The instruments manufactured by Kolberg Percussion GmbH, Uhingen, Germany are tooled on their outer surface to resemble natural log graining, no doubt contributory to their inflated cost. We are not reproducing this effect. Below are some study photos taken by Stuart of the Kolberg instruments

Photos by S Gerber

My drawing based on Stuart's field dimensions. (above) Process photos following. My addition to the original design is a reveal that occurrs around the top of the carcus that will allow us to easily interchange the top plate.

The larger of the two slit drum carcuses is dry-fitted. Showing the tracking grain from the end around to the side. Before assembly the sides will have the sound hole (slot, more like) routed.

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Routing the sound hole slot and clamping up the first carcus

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The larger of the two drums has the corners radiused and the rebate along the top edge has been routed.

Close-up of the rebate

Inside view of a typical end with the interior liner block angled back so as not to contact the top. Only the thin rebated edge contacts the underside of the top. The rebate ecreates a continuous edge to seperate the top from the carcus. This will be a hide-glue joint to make disassembly of the top easier.

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The carcuses are complete.

The template for routing the slot in the top.

One of the top slots for the small drum is cut

The small drum top is complete and is glued on to the carcus. I am using hide glue so the top can be easily removed should it need to be remade for repitching.

This is the top for the long drum, showing the rebate at the thick edge. The drums produce two different tones based in part on the thickness of the top. These are two boards of contracting thickness layed up. But because the top edge of the carcus is consistant, a rebate must be made along the thick side to flush it out with the thinner side. Through reverse engineering the Kolberg drums we discovered that the "soundhole slots" in the sides are infact not soundholes but primarily tuning slots. The longer the slot, the greater the ability for the top of that side to vibrate at a longer waveform and therefore a lower pitch. So we shall hensforth refer to these slots as "tuning slots". The enlarged openings in the top is more accurately the "soundhole".

The long drum is finished. I am using tung oil to finish them. I have recently had the epiphany of avoiding finishes with strong VOC's like nitrocellulose lacquer for natural finishes like tung oil, which has excellent water resistance and doesn't kill you.

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OK, now that we know how the "tuning slots" work, I have made another set of drums which are fully assembled before the slots are cut. Here is the jig I made to clamp to the finished carcasses to tap the 3/4" wide slot. The router is moved in increments of 5mm symmetrically about the centerline until the desired pitch is obtained.

The drums are complete.

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Bring it HOME.