When a musician is tasked with creating sheet music from a recording of an improvisation, and they write down the notes that make up that same music or instrumental solo, it is said that they have created a "transcription" -- they have transcribed to notation something that, in this case, was previously unnotated.
A transcription can also mean rewriting a written piece of music, either solo or ensemble, for another instrument or group of instruments for which it was not originally created.
A transcription therefore, strictly speaking, is not an "arrangement" -- it is a faithful adaptation, whereas the latter generally changes significant aspects of the original piece.
These terms tend to overlap in popular usage however; people speak of, for example, an organ "transcription" of Claude Debussy's Claire de lune from his Suite bergamesque for piano, "arranged" by someone.
A control provided to certain very large church organs and most large concert organs is the Pedal [Treble] Separation tilting tablet.
This control, also known as a Pedal Divide, permits the player more freedom in playing transcriptions -- it splits the sounds available on the pedals, usually at tenor C, by giving the 13 lower notes of any drawn Pedal stop, the rest of the pedalboard sounding any manual to Pedal coupling; many instruments with this feature are also equipped with a control to set the split point anywhere in the middle of the pedalboard.
This control is wired to silence the Pedal stops above the split point, usually at middle D or E, and silence the coupled manual stops below that, to free the right foot to play its own instrumental part on the pedals.
Because of the multiplicity of orchestral parts -- in an orchestral piece there may be as many as 2 dozen separate instrumental parts being played simultaneously -- it becomes problematic to reduce this music to what a single organist can manage to play; the purpose of this control is to supplement the technique of thumbing down on a lower manual to give as many instrumental parts as possible, if not the entire composition.
When the split point is adjustable it needs to be near the low middle compass of the pedalboard with the divide favoring a wider compass for the right foot so it can better carry its own melodic line (when the split point is non-adjustable it generally defaults at the C key in the middle of the pedalboard).
When this control is adjustable a "set button" for the Pedal Separation will be provided; the organist simply holds down the pedal key where the split point is desired, and, while holding down the key the button is pressed, and the new split point is set; Pedal stops would then play below that point, and above it would be whatever stops are coupled from the manuals.
This allows 4 different tone colors to sound without thumbing down across manuals [See blog, Thumbing Down] -- one in the right hand, one in the left hand, one with the right foot, and one (the bass) with the left foot.
The instruments at King's College, Cambridge and Gloucester Cathedral, Truro Cathedral, and Ripon Cathedral in England are all equipped with this control, and there are several examples from American organ building including, most notably, the monumental Wanamaker Grand Court organ in Philadelphia and a few others.
In the worship service this feature can be very useful when one wants to solo the anthem or hymn tune with a big reed; if the reed is taken by the left hand, the right hand harmony cannot be as full, but if the reed is coupled to the Pedal with the Pedal Divide engaged, both hands can play spread harmony on the Great for a much bigger sound while the right foot solos the tune on top half of the pedalboard and the left foot provides the supporting bass on the bottom half; both feet then, instead of assuming their usual role as a 3rd hand, in effect function as 2 extra hands each playing a single note.
In some instruments the big reed might also be drawn on the Swell with the Melody reversible Coupler engaged on the Great; this coupler permits whatever is drawn on the manual above to sound only in the highest note played by the right hand on the Great.
When the Pedal Separation feature is never used, its tilting tablet can be rewired and relabeled to function as something else not original with the builder which, depending on how the instrument is used, may be more generally useful.
This was done with the historic Kimball organ at the Saint Louis Scottish Rite Cathedral where the original Pedal Separation tilting tablet Kimball provided was rewired as a Master Swell Lock tilting tablet allowing all of its 128 swell shades to be operable from a single Swell shoe, simultaneously, thus bypassing the movable sliders in the center of the coupler rail above the Solo manual which were no longer functioning.
In this instrument 4 new Pedal to Manual couplers have been made optional additions to individual memory banks assigned to organists, if requested; these were not original with the builder and have not been made a part of the general definition of this organ's new computer control system [See menu bar, Photos III, Development & Design subpage].
These new couplers are operated by 4 tilting tablets located at the extreme right of the coupler rail above the top manual; these were originally designed as Crescendo tilting tablets.
These tablets, when so configured, read from left to right as: 1) Pedal to Swell (formerly Flutes to Crescendo), 2) Pedal to Choir (formerly Strings to Crescendo), 3) Pedal to Great (formerly Diapasons to Crescendo), and 4) Pedal to Solo (formerly Reeds to Crescendo).
In this instrument we find a type of design not uncommon for Anglo-American organ building of the time in which all Pedal voices save for perhaps one or two ranks -- in this case a single rank of 68 unified Bombarde pipes -- are borrowed from enclosed manual divisions whose 8-footwindchests have been extended for this purpose.
This means that, in this organ, the 4 new optional Pedal to Manual couplers are polyphonic and operate on all 61 notes of each manual.
These controls can be helpful to new organists who are coming to this instrument from the piano, may be hesitant to perform the pedals in public just yet, and gets them playing the whole instrument right away in so-called "keyboard style" where the right hand plays a 3- or 4-note chord and the left hand plays a single bass line.
In certain instruments, both pipe and electronic, the Pedal to Great coupler is sometimes labeled "Bass coupler" or "Automatic Pedal" (A.P.) and is provided with its own reversible piston (photo).
When inserted in an electronic instrument supplied with an independent Pedal division this coupler is often wired to be monophonic, i.e., operable on only the lowest note played on the Great and limited to the bottom 32 notes of that manual.
Also, in electronic instruments, the Pedal stops are often silenced on the pedal keys when this coupler is engaged, whereas on a pipe organ all of the Pedal stops (unless specially wired not to) will still sound there.