Reed Organ - Stops

Stops

Reed organs of European and U.S. design nearly always have a split keyboard, with one set of stop controls for the bass register at E3 and below and another for the treble.

The standard European configuration of stops for pressure-bellows instruments included five numbered draw-knobs for each register:

• An 8' foundation rank
• A 16' foundation rank
• A 4' reed-like rank
• An 8' reed-like rank
• A 16' soft, salicional-like rank

Because this specification was so widespread and the numbering of each type of stop was standard between manufacturers sheet music could be printed with the specific registrations to be used by the organist- something that could not be done to any great level of detail with music for pipe organs because of the great differences in specification between instruments.

This standard configuration was not found among U.S. instrument makers (and wasn't applied by European makers of vacuum-bellows instruments) which therefore varied considerably in their stop-lists, with the most common instruments having two complete sets of reeds and ten or more draw-knobs controlling various couplers and expression features. The main sets of reeds were invariably divided into Bass and Treble sections controlled by two separate draw-knobs to allow varying tones to be created on each half of the keyboard- for example, a 4' stop may be drawn on the Bass and a 16' of a different tone on the Treble, to produce two readily available sounds of the same pitch but of a different tonal quality, or a solo stop could be used on the treble with several stops together on the bass part of the manual providing an accompaniment. Alternatively both stops of the same pair could be drawn on each half of the keyboard to produce the same tone and pitch across the compass of the instrument. Stops that controlled a Bass or Treble section of a complete set of reeds often had numbers or other indicators on their faces to allow the player to tell which stops were paired.

As well as the main ranks spanning the entire compass of the keyboard, makers frequently added sets of reeds only playable on one half. A half-set of reeds may be provided (with its own draw-knob) to act in conjunction with another as a 'Voix céleste'. A set of reeds played only on the bottom-most octave of the keyboard and of 16' (or even on occasion 32') pitch was common on instruments intended for large churches or concert performances- such a stop was usually termed a 'Sub Bass'.

It was common for organ builders to provide multiple draw-knobs controlling each rank of reeds- for example, one draw-stop would open the mute over the reeds fully, while another would only open the mute half way when pulled, providing a softer tone.

Mechanical stops controlled various functions on the instrument. Octave Couplers were commonly fitted, where the key one octave above the key being pressed would also be pulled down. On larger instruments this function was split between the two halves of the keyboard- the Bass Coupler coupled the octave below the key being played, the Treble Coupler the octave above. A 'Forte' stop controlled the shutters over the reed ranks- when pulled a louder, richer tone was created. Larger instruments had the Forte mechanism doubled-up to allow separate control of Bass and Treble sections. A rare feature was 'Pedal Point'- when the draw-knob was pulled the organist could press a key in the bottom octave of the keyboard and the key would be held down once finger-pressure was released until another key was pressed. This went some way to compensate for the lack of a pedal-board. On some organs this feature was controlled by a knee-operated lever instead of a draw-knob.

On all but the smallest instruments a 'Vox Humana' or tremolant was a common feature. This is a mechanical stop which controls a vacuum-powered fan to disturb the airflow over the reeds and create the desired vibrato effect.

What with the splitting of the main reed sets, the duplication of controls for each set and the presence of mechanical stops means that while an instrument may only have 3 or 4 sets of reeds it may have as many as 20 draw-knobs.

Larger reed organs were made that had multiple manuals, and in some cases a pedal-board. These were sold primarily as practice organs to professional organists and to churches unable to afford or house a pipe organ. Since the pedal-board prevented the player pumping the bellows with his or her feet as on a smaller instrument such organs had a separate handle which an assistant would operate to produce the vacuum, or on later instruments an electric air pump. Instruments with more than one manual and/or a pedal-board would also feature coupling mechanisms between keyboards as on a conventional pipe organ.