About
About the Organ Stop Library
The Organ Stop Library is an online resource for those interested in hearing and studying organ stops. Organs of various styles and time periods are represented.
The "Individual Stops" Page
When you click an organ on the home page, the "Individual Stops" page opens in a new tab. Every stop of the organ is available as an "arpeggio" - from low to high beginning with the low C, E, G, c, e, g, etc. The recordings were made as from the ears of a listener in an optimal audience seating position - centered left to right, and less than half-way back.
The "Stop Combinations" Page
To hear important stop combinations, click a "Stop Combinations" link. A few measures of the hymn tune, "St. Anne" is available for most 8' stops, some 4' and 16' stops, and various common stop combinations (8' and 4', 8' 4' and 2', 8' 4' 2' and mixture, etc.). Most recordings are played manual only, and some include pedal. In every case, all stops used in the recordings are clearly identified. For some organs, a recording of the first pages of a Buxtehude Praeludium registered in some form of the plenum is available for comparison.
For most organ students, teachers, researchers, and builders, the greatest value of this library may be to hear and compare recordings of diverse stops and combinations within an organ and between various organs. Opening audio files in new windows and hearing side-to-side comparisons can be very informative.
The Relative Intensity of Organ Stops
"The relative intensity (that is, volume) of organ stops" has been the main focus of this project. The main goal was to provide recordings through which the intensity (volume level) of stops and combinations might be compared. For this reason, when you open a recording of an individual stop, an x/y graph is often shown with three lines that represent that stop in three ways.
GREY DASHED LINE. This line connects the points representing the actual volume of each pitch. These lines are always jagged, since the voicing process usually relies on the voicer's ears alone. Perhaps more importantly, the volume measurements change rather significantly with a change of microphone placement - mainly due to acoustics. For those reasons, two additional lines are shown (see below) that attempt to follow the overall direction or "slope" of the stop's volume. It is likely that these lines lines reveal more accurately the organbuilder's overall intent in voicing each stop.
GREY SOLID LINE. This line, beginning at note 3, shows the average volume of that pitch and the two previous pitches. This line is somewhat smoother than the grey dashed line, offering a better idea of the intended overall volume progression of that stop.
BLACK SOLID LINE. The black "trend line" shows the general slope of all pitches, as calculated by a polynomial curve-fitting algorithm, to more closely follow the average volume levels. In a few cases an additional graphic is given with one or two of the most extreme actual pitch levels removed, or with a straight-line algorithm.
To demonstrate how the volume levels were derived, see the original waveform graphs below. The negative numbers on the Y axis - to the left - of each graph represent decibel (db) levels (intensity, volume). Points were plotted along the waveform that appeared to accurately represent the "settled-in" volume level of each pitch. In the graph below, for example, low C is -34.73, low E -34.16, low G -31.00, etc. Note that on these graphs, the negative db readings for each pitch are given as positive numbers for simplicity.
A careful look at the these points reveals that they cannot be considered absolute or definitive. Various analyses would produce slightly different actual numbers, within a small range, but even with those variations the volume and general slope lines change only slightly.
A small range of possibility also exists in the "St. Anne" audio clips.
For each "St. Anne" example, a point was chosen representing either 1) the highest volume of the example, or 2) the stabilized level of the final chord. Note that the volume level changes rather significantly even as a single chord is sustained. This change is attributed to the building acoustics, and would produce different readings with only slight changes of microphone placement in the space. For that reason, the given volume levels are only approximate and cannot be considered absolute or definitive.
In the Tables
For each organ, as described above, two pages containing various tables are offered. These tables offer: 1) the average volume of each stop or combination, 2) links to audio clips, and 3) a listing or description of the stop(s) sounding in each clip.
NEGATIVE AND POSITIVE NUMBERS. Because negative numbers are more difficult to work with when comparing volume levels, in the tables they have been adjusted equally within each organ to become positive numbers. For each organ, the stop with the lowest average db level (that is, the largest negative number) is noted. In the case of the Jacobi Schnitger organ it is the "Trecht. Regal" at -41.03. A number is added to that and all other stops and combinations in that organ, in this case 42, so that all of them are represented by a positive number. The average volume of the Trecht. Regal, then, becomes +.07 (-41.03 + 42). That adjustment number is the same for all stops and combinations within that organ, but is different for each organ.
COMPARING VOLUME LEVELS. For this and other reasons, the "relative intensity" comparison is only valid within the stops and combinations of one organ. One cannot compare any volume level measurements between different organs. For example: comparing the volume level of the Octave 8 and Octave 4 in the Schnitger Jacobi organ would be valid, but comparing the volume level of that same Octave 8 with the 8-foot principal of any other organ would be meaningless. Comparing the tone quality of stops between organs, however, would be of value.