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Special features of the MTH organ

The Melbourne Town Hall pipe organ, and its virtual version, has a range of special features not usually found in other organs. The vast array of possibilities these features present can be a great aid to the organist / musician. In this blog post we will cover some of the more interesting, and perhaps unusual aspects and features.

Back to historic times - the 1929 Ventil button

As you probably already know the history of this grand organ, built by Hill, Norman and Beard in 1929, a significant restoration and extension effort was undertaken during the 2000-2001 reconstruction by the Schantz Organ Company - USA. In fact, 4181 new pipes were added to the existing 5411 bringing the organ close to double its original size, now having have 115 voices and 150 ranks. There is a small piston (button) on the console, labelled “1929 Ventil”, that instantly transforms the organ back to its original state by disabling stops added in the extension.  Press the button, and the difference is clearly audible. This button works independent of saved registrations and crescendo settings, and can be enabled or disabled at any time during your performance. It can also immediately make your registration historic and you can check how it would have sounded in the previous state of the grand organ.

Divisions, keyboards and assignments

In view of the wide variety of control options provided by the MTH organ, a clear understanding of stops, ranks, divisions and keyboards is essential. 

In this blog post we define a rank as a group of pipes with similar sonic properties; stops as the means (with drawstops, tabs, switches etc.) to activate a selection of ranks in part or as a whole as you play the organ; divisions as sets or groups of ranks and stops; and keyboards as physical playable interfaces that are or can be assigned to specific divisions (so we have, for example, the Choir division assigned to the lower or first keyboard, the Great division to the second keyboard, and so on).  

Keyboards played by the hands are more commonly known as “manuals”, and that by the feet as a “pedalboard”.  On many real organs, the division to keyboard assignment is hard-wired and fixed; for example, the first keyboard (or manual) is playing, and always plays the ranks of the Great division. On some newer organs this assignment or mapping can be done adaptively, for example, there is a button that swaps the manuals assigned to the first and second divisions. The MTH organ has this feature and it is replicated in the virtual organ, swapping Choir and Great divisions.  This can be very useful when you play some German or French style organs, which have an opposite assignment on these manuals.

On the Melbourne Town Hall organ there are fixed division-to-keyboard assignments, and variable assignments which connect so-called floating divisions to one or more of the physical keyboards. Due to the fixed assignment the division and keyboard names are often used synonymously - hence Great division - Great manual, Swell division - Swell manual etc. In the virtual version, however, there is a clear difference between keyboard names and division names, as well as in their behaviour. In the virtual version, all divisions are floating but some of them are assigned, by default, to a given keyboard. This assignment can be changed in the Keyboards tab of the virtual organ. The Keyboards tab is most useful for organists having physical (MIDI console) interfaces with less than 4 manuals and pedal, for here they can conveniently and simply assign divisions to the available keyboards, and can also transfer their registrations and alter their settings easily when moving between different physical environments (i.e., between two different virtual organ consoles, one smaller and one with more keyboards).

It is worth noting that there is a difference between assigning multiple divisions to a single keyboard, and coupling them. Although the coupling function can also be technically realised by assigning two divisions to the same keyboard, couplers are still recommended to be used wherever possible - since this is the means most commonly employed in practice, and facilitates the transfer of registrations to another organ console.

Advanced coupling features

Although the physical pipe organ of the Melbourne Town Hall has a carefully selected and very versatile set of couplers, Inspired Acoustics decided to implement a full coupler matrix between all divisions in the virtual version. The full coupler matrix means (almost) anything can be coupled to (almost) anything in any way desired. The coupler matrix is seen under the 'Couplers' tab.

Coupler types and terms

Before going through the features, let us briefly cover the terms we use here to label couplers. First of all, couplers are defined in this organ between divisions. This means that regardless of the mapping of divisions to keyboards, the coupler between the Great and Swell divisions, for example, will always remain operating between Great and Swell divisions, regardless of whether keyboard 3 was assigned to Great and keyboard 1 to Swell, or any other assignment. This ensures your registration and coupler selections will always work the same way regardless of how your virtual organ console is set up.

So we have inter-divisional and intra-divisional couplers. Some may know these as inter-manual and intra-manual couplers, but since we work with couplers between divisions, as mentioned above, and not couplers between keyboards, we use the term divisional.  In this context inter-manual couplers would work between physical keyboards, not logical divisions.

Let us cover the definitions then that apply to the MTH virtual organ.

Inter-divisional couplers are those that make a connection between different divisions, for example the ‘Swell to Great’ is an inter-divisional coupler.

Intra-divisional couplers are those that operate within a division; these are the 'Octave' and the 'Sub Octave' couplers. For example, a Great 'Sub Octave’ coupler affects the sounds of the Great division only, by adding notes an octave below those that are being played on the keyboard assigned to the Great division, and similarly for the 'Octave' coupler except that notes are added an octave above those played. The Unison Off could also be considered an intra-divisional coupler, the use of which is normally associated with that of sub and super octave couplers. It differs in application in that by default the coupler is On or active, and couples a division to an assigned keyboard at unison pitch. Activating Unison Off uncouples this unison connection of division to physical keyboard. In use it allows the sub or super octave coupled ranks within a division to sound without those ranks also sounding at unison pitch.

We call straight (divisional) couplers (or unison couplers) those couplers that implement a connection between two divisions without transposing or altering the polyphony of the sound.

Transposing couplers, on the other hand, couple divisions using an octave transposition (for example, Swell to Great Octave - the Swell division is coupled to the Great division but at an octave higher in pitch).

Couple alternators change the polyphony of the coupling mechanism, for example they couple only the single highest note (called the ‘Melody’ coupler) or only the single lowest note (called a ‘Bass’ coupler) when playing a chord. This can be useful to support a melody or bass voice when playing complex texture of music.

Reverse couplers are those that couple the pedal division to a division that is meant to be played on a keyboard. This coupler is useful in situations where a pedal board is not available, or for improvisations that needs extreme versatility.

Propagating couplers - neither the actual MTH organ nor the MTH virtual organ have so-called propagating couplers.  That is, a coupler that couples through to another coupler such that if Division 3 was coupled to Division 2, and Division 2 is coupled to Division 1, then notes played on a keyboard assigned to Division 1 would play simultaneously Division 3, Division 2, and Division 1.  On most organs, that is those without propagating couplers, the example coupling described above would result in only Divisions 1 and 2 being played from the assigned keyboard - Division 3 would not be played.

Now that we have the definitions in place, let us go briefly through how couplers actually work in practice in the Melbourne Town Hall virtual pipe organ.

The 'couplers' page is divided into rows and columns. Rows denote targets, while columns are for sources. For example, in the row of ‘to Swell’ all couplers will be coupling something to the Swell division. You can see various buttons and labels there.

  • Spl: this is the abbreviation for ‘split’. Split coupling ...
  • M and B are Melody and Bass couplers. They change the behaviour of the neighbouring associated couplers
  • Octave and Sub Octave couplers are transposing couplers corresponding to the nearest straight coupler (e.g. Swell to Great) displayed on the page. They work independently of the straight coupler, so the ‘Octave’ near the Swell to Great coupler is a Swell to Great octave coupler, just its label is abbreviated.
  • Unison Off turns off the sounds of a division sounding at normal pitch, that is the pitch defined by stop designations. This allows octave coupling (Sub and Octave) of stops to sound alone.

Floating and non-floating divisions

Although all the divisions in the virtual organ are floating, the real organ has some that are non-floating divisions only, these are the Pedal, Choir, Great, Swell and Solo divisions. The non-floating divisions are permanently assigned to specific keyboards (manuals and pedal board) on the real organ. By default the virtual organ mimics the non-floating division assignments of the real organ. These assignments can be seen under the Keyboards tab of the virtual organ.

The remaining floating divisions in the virtual organ (Orchestral, Bombarde, and Fanfare) may by default be unassigned to any divisional keyboard. They can be freely assigned using the 'couplers' screen, or from the Keyboard tab. The actual MTH organ has, by default, the Bombarde division coupled to the Solo division, but may be coupled to each or all of Choir, Great, Swell, and Solo divisions; and the Fanfare division is coupled by default to the Great division by operation of a foot piston; it too may be coupled to any other division. The Orchestral division is initially without coupling to any other division.

Floating divisions are coupled by assignment to a particular divisional keyboard or manual. Every function relating to a particular floating division is active and available when assigned to a division keyboard. It will be noted that the Orchestral division has sub and super octave coupling, and a Unison Off, all represented on the 'Centre' screen; all these functions apply when playing from the coupled keyboard, which in the case of the Orchestral division, can be any one or all of the assigned divisional keyboards.

Enclosure of divisions

There are three (3) principle shuttered chambers in the MTH organ.  These contain the Swell division, Great (partial) and Choir divisions - a shared chamber, and Solo and Orchestral divisions - a shared chamber.  A single set of shutters for each chamber allows expression of the Swell division alone, Great and Choir divisions combined, and Solo and Orchestral divisions combined.  Each of the three sets of chamber shutters is assigned to its own single expression pedal, thus Swell, Great-Choir, and Solo-Orch expression pedals.  Implementation in the virtual organ allows each division to be separately expressed, however mapping to mimic the real organ can be readily achieved using the Keyboards tab.

Great division special features

The Great division has ranks unenclosed, but unlike usual practice, also many ranks in an enclosed section and under expression.  Those ranks enclosed can be separately transferred to and played with the Choir division as Reeds or Flues.  When transferred, these ranks are no longer available to be played with the remaining unenclosed ranks of the Great division.  The controls of this transfer are labelled "Enc Great Reeds to Choir" and "Enc Great Flues to Choir".  The 'flues' include all enclosed ranks other than reeds.  When these ranks are transferred to the Choir division they come under the influence of the Choir intra-divisional coupling - sub and super octave, and Unison Off; however they remain exposed to the Great divisional Tremulant, and Great division expression control.

Color coded couplers

You can notice that some of the couplers of the virtual pipe organ are either shining in yellow or in white light when enabled. In fact, every coupler that has a copy on the Center page has this option. The color codes work as follows: once a coupler has the Bass or Melody modifier enabled, the coupler will be yellow when turned on. This helps you immediately see that the coupler behaviour is altered. If neither Bass nor Melody is enabled, the coupler will shine in white color when engaged showing its original, unaltered behaviour.

Divisional cancel buttons

In the virtual version of the organ, you can find a divisional cancel switch embedded in the Label of each of the Divisions. This is available only in the 'Centre', and 'Left' and 'Right' screen displays (as well as in other large Inspired Acoustics virtual pipe organs, such as the PAB).

Human voice specialties

There is a certain stop in the Swell division of the organ, called the Vox Humana 8’ which has two special features not very often found in pipe organs.

Firstly, the Vox Humana 8’ is embedded in two layers of swell enclosure as its pipe are built inside a dedicated shuttered swell box located inside the Swell chamber, which also is a swell enclosure. This swell-within-a-swell enclosure gives further performance possibilities and is activated using a dedicated stop switch “Vox Humana Mute”. The Vox Humana shutters are either fully open or fully closed.

Secondly, there is a dedicated tremulant engine for the Vox Humana which is activated separately from the Swell division tremulant. This can be triggered by the Vox Humana Tremulant stop switch. Naturally, the tremulant has a different effect when the dedicated swell box is activated or deactivated. It was indeed a challenge to implement this in the virtual pipe organ.

4K resolution and more

Clearly a feature of the virtual version only, the most important screens (pages) of the Hauptwerk version of this virtual organ are available rendered in 4K landscape resolution as well. This enables projection to modern large screens as well as to building facades in high quality. Also, for daily use, this higher resolution very well adjusts to your actual screen resolution, either it needs downsampling or, perhaps, upsampling. Portrait screens are available in full HD and for compatibility reasons, a regular SXGA landscape resolution at 5:4 is also provided. Resolutions applicable will depend on the window size and screen size of your current setting and will change on-the-fly as you resize the screen or window.