Jul 27

Letter from Henry Willis to Ernest M. Skinner

Mr. Ernest M. Skinner
Aeolian-Skinner Organ Co.
Boston,
U.S.A.

My dear Skinner:

In answer to your letter and query about width of mouths used for Great Diapasons, and “conventional” wind pressures etc. I have no standard, every job having its scales, mouth widths and pressures designed to suit the acoustical properties of the building and the same applies to wind pressures, but in respect to the latter, 4-1/2″ is the pressure which, on the average, is most used for Great Diapasons.

Reference scales, mouth widths and pressures I give you details of some typical jobs:

Westminster Cathedral
“Good acoustically”

Great scale mouth wind
Open Diapason No. 1 8ft 7-3/8″ 4-1/2″ 12″
Open Diapason No. 2 8ft 6-1/2″ ²⁄₇ 4-1/2″
Open Diapason No. 3 8ft 5-7/8″ 5 4-1/2″

Sheldonian Theatre Oxford “Medium acoustically”
(Not a Theatre but a semi-rotunda University Hall)

Open Diapason No. 1 8ft 7-1/8″ 4 6-1/2″
Open Diapason No. 2 8ft 6-1/2″ 4-1/2 3-1/2″
Open Diapason No. 3 8ft 5-3/8″ ²⁄₇ 3-1/2″
Open Diapason No. 4 8ft 4-3/8″ 4 3-1/2″

Sheffield City Hall
“bad acoustically — Reverberation period empty 1/2 second””

Open Diapason No. 1 8ft 7-3/8″ 4-1/2″ 10″
Open Diapason No. 2 8ft 6-1/8″ ²⁄₇ 5″
Open Diapason No. 3 8ft 5-3/8″ 5 5″

and so I could go on. There is no standard design etc. depends entirely upon the needs of the building. Generally speaking it is safe to say that the use of 1⁄2 mouths is unwise for high pressures (over 5″) or for buildings with a low reverberation period.

In addition each Diapason has its own special treatment as regards its construction whether the lower lip is “punched,” “half-rounded,” “flat,” or “long flat.” Also languids vary in type and thickness according to requirements.

Reference Swell Organs: for moderate sized 3 manuals I often place all on one pressure which may be 5″, 6″ or 7″ according to requirements – those of the reeds governing the pressure for there is no difficulty in adjusting the flue work to suit. When I want the chorus reeds on 8″ or more I use a lower pressure for the flue work, 5″
” being a nice pressure.

By “pocketed shallot” you mean what we call “filled in.” Yes, I use this type of shallot when refinement is called for. 16ft Waldhorns nearly always have filled in reeds, unenclosed Tubas for medium sized buildings generally filled in reeds, families of Great Trombas usually have filled in reeds  — Trumpets never.

Don knows all this and was perfectly conversant with the reasons governing the selection of scales, mouth widths and pressures for Diapasons — also the use of filled in reeds.

Yours ever,
H.W.

H.W./K.C.