Parish Organ

How to read the specifications for Letourneau Opus 98

Letourneau Opus 98 has four divisions: three manual divisions played by the hands, and the pedal division played by the feet. Each part of the specification refers to the stops played on those keyboards respectively.

The name on the stop refers mainly to function or musical color. Some organ stops are nonimitative and produce foundational organ tone, e.g. Diapason, Principal, Octave. Others resemble wind or string instruments, e.g., Chimney Flute, Harmonic Flute, Gamba, Trumpet, Oboe, Trombone.

The numbers following the stop names refer to pitch as a function of the length of the longest pipe in the stop. Eight foot pitch is unison pitch. It agrees with the pitches of the corresponding keys on the piano, for instance. The science of acoustics works on the simple principle that halving or doubling the length of a vibrating body changes its pitch by an octave. Therefore, the shorter and longer designations after stops indicate the pitch at which they sound. The combination of these with unison stops produces the complex ensemble sound of the instrument.

Stops with a Roman numeral following the name, or mixtures, correspond to the upper harmonics of the overtone series and have multiple pipes per note tuned to these overtones.

The second number after the stop name, in the rightmost column, refers to the number of pipes in the entire compass of the stop, or the rank. Ordinarily, a complete manual stop would have 61 pipes, corresponding to the 61 keys of a manual keyboard. Where fewer are indicated, the stop may be an extension of another stop at another pitch (extensions often have 12 pipes to finish a bottom or top octave), or it may be incomplete for some particular reason. Occasionally, stops will play in more than one location in the instrument and these are indicated by the name of the home division in the final column.


Specifications

GREATCHOIR
Double Open Diapason16Lieblich Gedeckt16
Lieblich Gedeckt16Metal Gedeckt8
Open Diapason8Gamba8
Second Diapason8Flute Celeste II8
Harmonic Flute8Principal4
Stopped Diapason8Spindle Flute4
Principal4Octave2
Open Flute4Larigot1 1/3
Fifteenth2Sharp Mixture III-IV1
Cornet III (TC)2 2/3Cremona8
Mixture V1 1/3Callaway Tuba8
Trumpet8Tremulant
Tuba8Choir 16'
TremulantUnison Off
Great 16'Choir 4'
Unison Off
..
SWELLPEDAL
Diapason8Contra Bourdon32
Gedeckt8Open Wood16
Salicional8Double Open Diapason16
Salicional Celest (CG)8Bourdon16
Principal4Lieblich Gedeckt16
Chimney Flute4Major Octave8
Nazard2 2/3Metal Principal8
Spitz Flute2Bourdon8
Tierce1 3/5Lieblich Gedeckt8
Full Mixture V2Choral Bass4
Double Trumpet8Mixture IV2 2/3
Oboe8Contra Trombone32
Clarion4Double Trumpet16
TremulantClarion4
Swell 16'Tuba8
Unison Off

Summary Table

DivisionStopsRanksExtensionsBorrowsElectronicsPipes
Great131612-940
Swell14162--993
Choir11141--826
Pedal179461336
Total55558813098