The Woehl Organ at Studio Acusticum

A magnificent new pipe organ, often called the “organ of the future (zukünftige Orgel),” has been built by Gerald Woehl for the Studio Acusticum Concert Hall in Piteå, Sweden. The experience of playing it is like having two or three world-class organs at one's fingertips. This webpage is intended as a resource for organists who will be performing on Organ Acusticum, based on information that I gathered during my visit to Piteå in January 2017.

A bit of history and context

Gerard Woehl, who has extensive experience with organs in both French and German styles, founded his Orgelbauwerkstatt in Marburg in 1966. Before this project he was perhaps best known as the builder of the 61-stop Bach Organ (2000) in Leipzig's Thomaskirche, as well as the restorer of many historic instruments. The Acusticum organ, at 91 stops, is his largest project to date. (Indeed, it is one of the largest pipe organs in all of Scandinavia.)

Piteå is a charming town in northern Sweden, with about 25,000 inhabitants. It is less than an hour's drive from the busy airport at nearby Luleå. Its School of Music, founded in 1978, is affiliated with Luleå University of Technology. The city of Luleå — or more precisely its nearby suburb Gammelstad — is also the home of Grönlunds Orgelbyggeri, another maker of exceptional instruments; therefore many fine Grönlund organs exist in the vicinity of Piteå, and there is a strong local tradition of excellence in organs.

In 2007, the municipality of Piteå opened Studio Acusticum, a versatile wood-paneled performance space with (surprise?) fantastically good acoustics, adjacent to the School of Music. The 500 seats in its concert hall have been cleverly designed so that the sounds heard by an organist when practicing in an empty hall are essentially the same as the sounds heard when the hall is filled with people.

I stayed at Piteå Stadshotell, a comfortable and well-run hotel of 111 rooms, built in 1906. It is almost exactly one mile away from Studio Acusticum, via a pleasant walk along Nygatan. Piteå also has four or five other fine hotels. (Be sure to try the local specialty, “Pitepalt,” which pairs perfectly with the beer that's brewed a few blocks away.)

Introduction to the organ

The underlying philosophy of Organ Acusticum, as it was conceived by Hans-Ola Ericsson when he was still a professor at Piteå's music school, was to provide an eclectic mix of historic European traditions, in combination with modern innovations that will inspire 21st century experiments in sound. It has fifteen windchests deployed in six divisions:

The Positiv features timbres of middle German provenance, while the Récit features French sonorities; the Hauptwerk and Pedal provide both; the Solo and Cornetwerk provide additional variety and spice. You can mostly guess the builder's intentions for any particular stop from the nomenclature: For example, the Postiv has a ‘Principal’ while the Récit has a ‘Diapason’. The major string stops of the Hauptwerk are ‘Viola da Gamba’ (mitteldeutsch) and ‘Violoncelle’ (französisch). Its major flute stops are ‘Rohrflöte’ and ‘Flûte harmonique’; it also has a (French-style) ‘Bordun’. Prominent reeds are its ‘Trompete’ and ‘Trompette’.

All four manuals and pedal are connected to the pipes via trackers that have a nice light touch. Some of the coupling between manuals is handled electrically. It is very pleasant to sit at the console, “directly attached” to the pipes; however, one must keep in mind that the Positiv is perceived more directly by the audience than it is by the performer, because of its position as an Oberwerk. (Incidentally, every pipe in the façade is a genuine, speaking part of the instrument, except for the three largest pipes in the middle.)

The organ was inaugurated in October, 2012, with five days of recitals by internationally renowned performers. Kimberly Marshall's article “The ‘Organ of the Future’ in Sweden's Studio Acusticum” [The American Organist (February 2013), 62–65] contains a wonderful description of those dedication ceremonies. As she says,

This instrument is intended to provide compelling performances of repertoire as well as to provide inspiration for new music. … Because of its large size, the Acusticum organ functions as several organs in one, with stops and registrational features to render Baroque, symphonic, and modern organ music. … All [participants in the inaugural symposium] were inspired by the sonic possibilities of the Acusticum organ and the creative avenues it opens for our instrument in an increasingly technological world.

Stops, combinations, and sequences

Of course the most important issue for performers is the ability to choose appropriate registrations and to switch between them conveniently when needed. Fortunately, the Acusticum organ has a flexible combination action, which handles this task as well as any organ that I've ever had the opportunity to play.

As you sit in front of the keyboards, you have easy access to two banks of stop-tablets, one on each side. At the left are the stops for the Hauptwerk and Pedal, numbered 1–104; at the right are those for the Solo, Récit, and Positiv, numbered 105–208:

(Click to enlarge any of these three images.) Notice, incidentally, that each manual extends all the way to high c, and the pedal goes up to high g. (Hooray.) There are three swell shades: The controller at the left is for manual IV, the one in the middle is for manual II, and the one at the right is for manual III. (This makes good sense, because it allows you to adjust IV–II simultaneously, as well as II–III.) A crescendo pedal or “Rollschweller” appears at the left of the swell controls; it is discussed below.

A stop is activated by pushing on the corresponding stop-tablet. A green light then goes on. For example, in the picture above, only three stops are active, namely numbers 144, 155, 156. (These are the Bourdon 16, Septième harmonique 1 1/3, and None harmonique 7/8, in the top row of the stops for the Récit manual III. It's a strange combination, but actually worth a try!) To deactive a stop, just push its tablet again. Several stops can be changed at once, by doing an appropriate “tablet glissando.”

Such button-pushing obviously takes excessive time, in the midst of a piece, so you'll want to pre-set most of the combinations. Here's where you get to use the handy little black box that sits in front of the right-hand control panel: This box has a touch screen, on which you can log in and record the combinations that you want, for each piece that you want to play. Details of that setup procedure are explained below. Nobody else will be able to interfere with the sequences of combinations that you specify.

Once you've got a sequence of combinations installed, you're ready to go. Notice the ‘0000’ in green lights just above manual IV in the photo above: That is your current position in the sequence. Altogether ten thousand combinations, numbered 0000 thru 9999, are available, for any one piece; hence you'll never run out. And you can set up separate programs for an essentially unlimited number of pieces, each identified by its name.

If you look closely at the photo above, you'll see that several other numbers are also displayed in green lights. (You probably won't make any use of them; but I may as well explain what they are, in case you're curious.) At the left of ‘0000’ in the illustration, which is the all-important current sequence number, there's a two-digit number ‘00’. That's the current position of the Rollschweller, and it ranges from ‘00’ (no stops) to ‘61’ (all stops), as explained below. At the right of ‘0000’ there are three one-digit numbers ‘0’, ‘0’, ‘0’; ignore them! They were once intended to indicate the current settings of the three swell shades, and there had been some thought of allowing those shades to be controlled electronically. But at the present time they are always ‘0’, and the shades are 100% controlled by your feet alone. The only way to tell the amounts by which the shades are currently open or shut is to look at (or feel) those foot controllers.

Notice also the little white buttons that appear below each of the four manuals in the photo. Almost all of those buttons are labeled ‘▷’. Whenever you press ‘▷’, the current combination number advances by 1. (Also 9999 advances to 0000.) Those handy buttons are your friends, because one of your thumbs will almost always be near one of them. The photo also shows two dark brown, spherical toe studs above the pedalboard; those toe studs give you another way to advance by 1, when your hands are busy.

The little white button at the upper left, just below the bass notes of manual IV, is a exception: It is marked ‘◁’, not ‘▷’. And it decreases the current combination number by 1.

Furthermore, the left side of the left console and the right side of the right console have their own ‘▷’ and ‘◁’ buttons, which increase or decrease the current combination in the same way—operated perhaps by assistants who you may using to help you with registrations in an unusually complex piece.

A button labeled ‘R’ appears just below the treble notes of the Hauptwerk keyboard (manual I). This is the general-clear/reset button, which deactivates all stops.

A button labeled ‘S’ appears just below the bass notes of manual I. Ignore it; it's a relic of an older sequencing scheme that is inferior to the more versatile system that I shall explain below.

The picture also shows twelve curious levers, above and left of the pedalboard. These are somewhat awkward ways to activate the drums, gongs, and other percussion effects that belong to stops 92 thru 95. For example, to play the ‘Paukenwirbel’ when stop 93 is active, depress the lever in position A#.

Several other stops require special explanation: The amount of wind can be decreased in various ways using stops 96 thru 100 and 102. Stop 101 is MIDI, which unfortunately is not presently connected to much of the organ. Stop 103 will some day turn on a light somewhere; at present it does nothing. Stop 104 enables the Crescendo; this stop, and 101 (MIDI) can not be activated by the sequencer. Finally, stop 208, ‘Klangkloppen auf’, raises the roof of the Positiv, making it speak as a Baroque Oberwerk. This process takes about ten seconds, and the open roof naturally wipes out most of the effect of the swell shade.

Important: Here is a complete stop list, from 1 to 208, showing each name exactly as it appears on the corresponding stop tablet. This list also contains many important details; for example, it explains which ranks are extensions of others, and it precisely clarifies which stops can be coupled from one manual to another.

Details of the sequencing software

You will be given an official account and username by a system administrator, who will show you how to choose a password and log in via the touchscreen. (This sequencing software, developed by the firm of Otto Heuß, isn't especially user-friendly. But at least it is robust and workable. At first I found many of its operations confusing and unexpected, and I shall not attempt to give full details of its behavior here. Instead I shall describe a simple recipe that works.)

Logging in consists of several steps. First you press MENU, in the upper right corner of the touchscreen. Then you press LOGIN. Then you scroll down in the list of usernames until you find yourself and highlight your own name. Then enter your password and press LOGIN again. OK, you're in!

Next, select a piece by its name. If the piece is already in your account, scroll to it by using the ‘▽’ or ‘△’ buttons on the touchscreen. Otherwise press ADD, and use the touchscreen to type in a new name.

At this point you can proceed to play that piece, if its sequence of combinations has already been specified satisfactorily. But if you want to change its combinations—and in particular, if you want to specify that sequence in the first place— press EDIT now. That takes you into editing mode: You see a new screen that shows the current piece's title, the current number of preset combinations, and the current combination number. You're allowed to change the current combination number with the touchscreen's keyboard if you like. Below that number you'll see two buttons, ‘◁’ and ‘▷’, which move the sequence number down or up. And at the right of the edit screen are five buttons, labeled X, INSERT, DELETE, SET, and SAVE.

To set up or change the combination for sequence number 0001 of the current piece, make sure that the current sequence number is 0000 (or ‘000-’, which the system mysteriously shows you when you begin). Then adjust the stop tabs, by pushing them on or off as explained above, until the little green lights are lit precisely where you want activity. Then press SET.

At this point you have the desired combination 0001 all set up, according to the console lights. And you can play the organ using those stops, if you want to remind yourself how those stops sound. But combination number 0000 (or ‘000-’) still appears on the organ, and on the touchscreen; and the new combination has not yet been entered into the system, even though you've said SET! Beware: If you now try to advance by pushing one of the little white ‘▷’ buttons, you'll find to your dismay that the new combination has been lost! What is going on?

The secret is that, when you pressed SET, the SET button on the screen suddenly changed its color, so that it now is half-lit-up. This is the computer's way of saying “I am ready to set up the next combination, as soon as you confirm it.” You should now press ‘▷’ on the touchscreen. Then the combination number will advance to 0001, and the touchscreen will say ‘SET OK’. The computer is confirming that it has indeed set combination 0001 as you had asked.

Combination 0002 is specified in the same way: You push the console stop tabs until you've got what you want; then, while the current combination still reads 0001, you type SET; and the computer tells you that it's ready to go, by changing the color of the SET button; then you press the touchscreen's ‘▷’; and you're sitting at 0002, reading “SET OK”.

In other words, the only confusing thing is that the number is one too small when you press SET. (You can use this procedure to set combination 0000, but only if the organ displays 9999!) Furthermore, each setting is a two-step process; you must confirm your intentions after asking the machine to SET.

Incidentally there is no good way to jump from, say, combination 0100 to combination 0200 in the middle of a performance. You could press the ‘▷’ button a hundred times; but that not only is horribly slow, it also will play the Zimbelstern and/or the Glockengeläute whenever they happen to be active in a setting that you pass by! The only decent way to move from 0100 to 0200 is to go into EDIT mode and type 0200 as the desired combination number, without actually editing anything.

Editing mode also allows you to INSERT or DELETE. But those operations can be dangerous, and you use them at your own risk. Deleting a combination blanks it out, and that number will henceforth show up “gray” when it is the current combination number in the edit screen. Inserting a combination will renumber all combinations up to the next blank one; for example, if combinations 0002, 0003, 0004, and 0007 exist but not 0005 or 0006, you can insert between 0002 and 0003; the previous 0003 and 0004 then become 0004 and 0005, while 0006 stays blank and 0007 stays put. But this procedure can easily lead you into trouble. There's really no point in having blank combinations in the middle of a piece, because the sequencer does not skip over them when you advance the counter. So I advise you not to use INSERT and DELETE unless you are sure that you know what you're doing.

To leave editing mode, press SAVE. (Actually you can also leave it by pressing X. But this nullifies all the changes that you've made! Never type X, unless you want the computer to forget everything that you did since pressing EDIT. Nothing goes into the computer's permanent memory until you've SAVEd it.

Using USB sticks to store your combinations

Before you log out, you can ask the computer to write all the combinations in your account onto a USB stick (also called a pen drive or flash drive). Put the stick into the USB slot on the left side of the left-hand console; then, from the touchscreen menu, select DATA, then select ‘Setter to USB stick’. The machine will ask you if it's OK to clobber any of the setter-data that already appears on the stick; you have to say Yes. (Therefore, if you want to preserve any settings that you had before, you should have backed them up somewhere else.) There can be many other files on the stick, unrelated to this organ; don't worry, those files won't be touched. The computer will only change the files in a top-level directory named ‘Heuss’.

You can look at those mysterious “secret” files by putting the USB stick into your own computer, where they'll show up in the Heuss folder. That folder, in turn, contains a folder labeled by your username. And that folder contains two folders labeled Crescendo and Title. For example, if your username is Sebastian, your USB will contain two folders that your computer will know as ‘Heuss/Sebastian/Crescendo’ and ‘Heuss/Sebastian/Title’.

The Crescendo subfolder will probably consist of a single file called ‘1.xcc’, which I'll discuss later. The Title subfolder is more interesting: It contains a file ‘TITLE’, which lists the names of all the various pieces in your account, as they appear in the list that you scroll thru when logging in. [That file is in so-called XML format, and you can look at it if you know how. For instance, on a Mac you can open it with TextEdit.] More importantly, the Title subfolder also contains subfolders labeled say f and p, if you happen to have pieces entitled prelude and fugue (but no pieces that begin with other letters of the alphabet). There is one such subfolder for every letter that begins the name of at least one of your pieces.

Are you still with me? We're getting now to the good stuff. Continuing our example scenario, suppose that you do indeed have a piece called fugue. Then there will be a file Heuss/Sebastian/Title/f/fugue.xst on your USB stick. This is where the sequence of its combinations lives.

In other words, all the fruits of the labor that you put into setting the sequence of combinations for fugue has been saved in this so-called XST file. An XST file is a special kind of XML file, often used together with databases. You can try to look at fugue.xst with, say, TextEdit, if you like. But you'll probably be disappointed, because the relevant information has all been encoded into cryptic 52-digit hexadecimal numbers.

Therefore I've written a little program, XSTtoTXT, that you can use to convert that data into human-readable form. Click here to download the file xsttotxt.w, which is the CWEB source code for this program. From that file, a person who is familiar with Linux (say) can compile the code and create a program so that a Unix command such as ‘xsttotxt <fugue.xst >! fugue.txt’ will tell you the names of exactly what stops are on at every step of fugue. [If you know nothing about CWEB, ask a friend for help.] For example, combination 0000 in the photo above would appear in the resulting TXT file as the following sequence of four lines:
 144 III Bourdon 16
 155 III Septième harm. 1 1/7
 156 III None harm. 8/9

I've also written a companion program, TXTtoXST, which goes the other way. For example, the Unix command ‘txttoxst <fugue.txt >! fugue.xst’ gives you an XST file that's equivalent to the one you started with. And if you've used a text editor to make changes to fugue.txt, you'll get an XST file that incorporates those changes. Thus you can make corrections to your sequences of combinations on your computer, instead of consuming precious time at the console of the organ. (Click here to download the CWEB source file txttoxst.w for TXTtoXST.)

By the way, if you edit that TXT file in order to make changes, you needn't bother to type in the exact stop names. The program TXTtoXST looks only at the stop numbers. For example, if you want to modify the example TXT file above so that the Septième is replaced by the Tierce, which is stop 154, it would be sufficient to change it to the following four lines:
 144 III Bourdon 16
 156 III None harm. 8/9

(And you could also apply XSTtoTXT to the new XST file that comes from the edited TXT file; then you'd see that 154 is indeed the stop III Tierce 1 3/5.)

When you edit such a TXT file, you can freely insert any number of comment lines, which begin with a percent sign ‘%’. Such optional comments are ignored by TXTtoXST. They might be used, for example, to explain the goals of a particular registration, and/or to mention at which point in the piece the sequencer should advance to each particular combination. I use such comments in order to prepare hardcopy documention of the registrations that I've chosen, to keep in my personal files for future reference. Here, for instance, is a sample file acusticum-fantasy1-annotated.txt, which records the combinations that I chose in January 2017 when experimenting with Chapter 1 of my composition Fantasia Apocalyptica.

Reading combinations from a USB stick

Put your USB stick into the slot, and select DATA, as above. Then specify that input should come from ‘USB stick to setter’.

If your USB stick has a top-level Heuss directory, with your username as its subdirectory, and if it contains XCC and XST files previously written by the organ or by TXTtoXST, and if you keep your fingers crossed, the organ's computer will then load the corresponding combinations.

The Crescendo pedal

Finally, I've promised several times above to discuss the so-called crescendo pedal. The Rollschweller at the left of the three swell shades can be rotated with one foot, so that the two-digit number displayed at the left of the current combination varies from 00 to 61. Whenever stop 104 is activated, all of the stops that correspond to the current Rollschweller setting will be added to the currently active stops (unless of course they're already active, in which case they'll stay active).

You can customize the Rollschweller combinations, in a way that's similar to setting ordinary combinations. And you can also store them on a USB stick. Such settings are recorded in an XCC file, in the Crescendo subdirectory within your user directory, as noted above.

In order to understand typical Rollschweller settings, I wrote a program called XCCtoTXT, which is analogous to (and almost identical to) XSTtoTXT. Here, for example, is the default crescendo setting that I encountered in January 2017, as output by XCCtoTXT from the file 1.xcc.

If you take time to look at that list, you'll see that it turns on both couplers II-I and III-I already at step 01; and it starts to use 16-foot stops on manuals II and III already at step 16. Therefore the default settings turned out to be of very limited use to me, in the pieces that I was working with at the time, and I decided not to explore the Rollschweller any further.

However, when I got home I also wrote a program called TXTtoXCC, by which I now have the ability to customize the Rollschweller and make it just right for any desired piece, via a USB stick prepared on my own computer. If you want to play with this, here are the CWEB source files and [To create the corresponding C programs, one can say ‘ctangle xsttotxt xcctotxt xcctotxt’ and ‘ctangle txttoxst txttoxcc txttoxcc’.]

Notice that the Rollschweller isn't actually required to produce a “crescendo” effect. Each level is independent of the others, and level 00 need not be silent. A “randomized” Rollschweller might even inspire some terrific “modern” music—who knows?!

Future plans

Specifications have been drawn up for a new Harmonics division, containing 53 ranks tuned to overtones of the harmonic series, to be constructed in a subsequent phase of the Acusticum Organ project. Kimberly Marshall noted that such pipes will create “hitherto unforeseen possibilities of building new sounds.” However, such extensions are currently on the back burner and unlikely to happen any time soon. Top priority at the moment is to improve the MIDI capabilities.


A thousand thanks are due to Prof. Gary Verkade, for his wonderful hospitality during my visits to Piteå also for the two screenshots above, and for helping me get the facts straight. And thanks to my wife Jill, for the majority of the photos above.

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