Portative with two stops

g - c'''
8' 4'
440 Hz
Gregor Bergmann 2015
 
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Slider

Lorenzo da Firenze

Dà, dà, a chi avaregia - Intabulation - Veit-Jacob WALTER, Organetto: click here

Live Improvisation

on Alleluya [V. Iustus germinabit sicut lilium] - D-W Cod. Guelf. 628 Helmst., fol. 41-42
Veit-Jacob WALTER, Organetto, listen here

Sliders in Portatives

Among organs the portative holds a unique position as to range, portability, and flexibility of wind. These aspects are usually looked down upon as being restrictions for the player. But they challenge any artist to be creative within these limitations and maybe beyond. Along with a lack of good players willing to unearth suitable music from the archives and perform it to high standards, these have perhaps been the reason for the past neglect of the portative in high quality performances. Today we have excellent musicians performing highly complex and beautiful period music solo or in ensembles.

The makers of historical instruments have come a long way as well, and very interesting copies can be heard and seen. All makers of medieval keyboard instruments are confronted with the difficulty that no instruments survive from this period. The information necessary to build such an instrument has to be extracted from musical context, manuscripts, reports, paintings and carvings in stone and wood. Here as well, what seems at first a restriction later challenges the maker to invent what neither iconography nor manuscripts reveal to him. This is what I have recently done with a portative that has two sliders, a detail that can be observed in several paintings. In this article I will discuss how sliders have been interpreted in the past and how I put them to use in my instrument.

Bartholomäus Köln
Bartholomäus-Altars, Köln, ca. 1490/95 (Source: Wikimedia  (Public Domain))
Bartholomäus München
Bartholomäus-Altar, München, ca. 1501/03 (Source: Wikimedia  (Public Domain))

When studying these pictures, one cannot avoid the conclusion that the instruments are state-of-the-art. The craftsmanship is of high quality, with a slender case, delicate carvings, and embossed pipes. These are highly developed instruments, musically and technically as sophisticated as organs are today. The intelligently decorated cases house very complex instruments with keys as we still use them, pipes scaled as we still do, and the same genially simple slider system that is common in most of our organs as well.

The presence of sliders in small portable organs with one visible rank of pipes has provoked many ideas.  The most common explanation for sliders in portative organs is that they operate the bordun pipes. Another,  more interesting, idea is that a reed stop is hidden in the space between keyboard and toe board. Hickmann¹ mentions a third one, Koppeln, but one cannot be sure what he means by that. There are probably more explanations that I do not know of.

Of these three the first is the least likely I think. To begin with, since the largest pipes, the bordun pipes, are always in the bass, it would be easiest to turn them on and off  using the keyboard. That would be easily accessible for the player's hand and technically more elegant. Also, players inform me that in most cases the thumb can easily play the bordun.

The second possibility, a reed stop, accounts not only for the presence of the sliders (one for the reed, the other for the principal) but also for the large vertical distance between pipe toe and keyboard. A Regal could be placed here nicely. Marcus Stahl of Dresden has built such an instrument. It would be interesting to know more about the musical use and effect of his instrument.

The third possibility is that the slider is used for a second flue stop. The pictures show the tops of the pipes, usually in two rows², and a number of pipes that corresponds with the number of keys. In other words, there are not enough pipes for two stops. However, with the player or the treble case wall hiding part of the instrument, one cannot be sure about the treble end. If one were to add one octave of pipes to the top as an extension, and place them between the two rows in the treble, they would be hidden from an angular view.

Together with the other pipes, except for the bottom octave, this addition would provide a complete stop pitched an octave above the lowest note. Maybe that is what Hickmann meant when discussing ‘Koppeln’, as this system would have the same effect as an octave coupler. To make this possible the instrument would need a windchest and a high toe board to accommodate the intricate groovings, thus the thickness of the toe board would serve a purpose. In a ‘one-rank’ portative, a much thinner and simpler toeboard suffices. The grooves to connect the octaves would not be necessary nor would a windchest be needed.

Organ history shows us that the principle of using one rank of pipes for several stops has at all times been practiced by some makers. The earliest description I know of is of an instrument by an unknown builder in Prätorius's Syntagma Musicum³. He describes an ‘Alt Positiff’ with one rank of pipes yielding three stops:  2’, 1-½’ and 1’. Again this little organ has a thick toe board.

When asked to build a portative organ I started studying pictures and soon began wondering about the sliders and the thick toe boards. I had been working in a shop restoring organs made by Daniel Hertz and even building new chest-organs using ‘Hertz’s’ system. When thinking about portatives, the ‘Alt Positiff’ and Daniel Hertz came back to my mind. So the obvious thing to do was to build a portative with two stops. My customer and I settled on an instrument ranging from 8’g1-c3 with two stops, 8’g1- c3 and 4’g2- c4.  A transposing mechanism for 440Hz and 466Hz further complicated things, thus a c# pipe was made (for c at 466Hz) giving a total of 45 pipes. The pipes from g1- c3 stand in front and back, staggered as usual in portatives, and the extra octave, c#³- c#4, stands between the two rows in the treble, as mentioned above.

The toe board is made of multiple layers of linden wood. The layers closer to the chest connect the octaves, the upper layers distribute the wind to the pipes. When laying out the toe board great care has to be taken to make sure that all the grooves leading to a pipe are of equal length and cross-section as much as possible. Otherwise it will be difficult to get the octaves in tune.

One great musical advantage of portative organs is that the player controls the wind pressure. For the organ builder that can cause trouble with unsteady wind pressure. It makes voicing a real challenge. With two stops forming a plenum sound, the tuning supplies another difficulty. There is a range though, rather than a point, within which the stops are in tune. Well voiced pipes tend to tolerate more changes in wind pressure without sounding out of tune. Still, some generosity is called for.

From a technical point of view the instrument works nicely. I am curious to learn what its musical effect or use will be.

 

 

1 Hans Hickmann, "Das Portativ"  - I am sorry for not being able to cite the exact page, the book being out of my reach.

2 There are also instruments with three ranks from the bass up.

3 Michael Praetorius, Syntagma musicum, Organographia, chapter XLVIII, p. 79-80. How the 1-½' register would have been used is an interesting question in itself, because of the tuning system used.