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!! NEW ARTICLE !! - The Vox Humana stop on the Gabler organ at Weingarten Abbey
Joseph Gabler's remarkable organ of 1750 at Weingarten Abbey incorporated a Vox Humana stop considered so lifelike that its origins quickly became rooted in legend. It remains celebrated today, thus prompting this article. Its pipes were found to have a high frequency formant ascending from 1.8 kHz to 4.4 kHz over the note range analysed (tenor C# to top A nearly three octaves higher). Hence the formant frequencies vary by a factor of only 2.4 for a note frequency ratio of 6.4, following a logarithmic law across this range. Thus the similarities to the 'singer's formant' present in the voice of a trained adult male singer were striking. This occupies a band around 2 - 3 kHz and, as with the Vox Humana, its frequency is relatively static compared with the tessitura of the singer. The formants of both the Vox Humana and singers also lie within the frequency band in which the ear is most sensitive, endowing them with similar penetrating abilities.
It is further shown how the formant arises from the fractional-length resonating tubes used across the rank, and how its frequency for a given pipe can be deliberately selected by promoting a coincidence between a specific harmonic of the vibrating reed and a specific natural resonance of the tube. Thus it is likely that Gabler had learnt how to precisely select and maximise the loudness of his chosen formant for each pipe through careful tuning of the tube relative to the reed just by using his ears. The Q-factors of some formant resonances were surprisingly high, resulting in SPL enhancements of several tens of decibels relative to the local mean levels in the spectra. It is a tribute to Gabler's obvious skill and an exquisitely keen ear that he was able to achieve this outcome. His Vox Humana at Weingarten does indeed have characteristics objectively similar to those of the human singing voice, even though it seems to have taken nearly 270 years to prove it.
These results are comparable with those from a previous analysis of the Vox Humana rank on a Wurlitzer theatre organ from the 1930s, also discussed in the article. This too is a striking example of the genre, and it makes one wonder whether and how the insights of master organ builders of the baroque era such as Gabler might have been handed down in some way through the craft to their successors some two centuries later.
The literature on musical temperament is replete with descriptions of keys which are said to be 'intolerable' and therefore 'unusable', and presumably such statements are intended to apply to all keyboard instruments. However this generalisation benefits from closer scrutiny, because not all instruments are the same where temperament is concerned. In particular, the many timbres or tone colours of the organ enable the key flavours of an unequal temperament to sound significantly different depending on which stops are used. This article uses audio examples to show that the differences can be remarkable, such as the case where even the notorious Wolf interval in quarter-comma meantone tuning becomes quite docile and usable when suitable stops are selected. These effects are unique to the organ because no other instrument has its wide range of tone colours and combinatorial possibilities.
It is shown why this interaction between temperament and timbre occurs by explaining firstly how key flavour is influenced by the beats of tempered consonant intervals, and then how the beats arise from specific pairs of harmonics in the notes defining each interval. It is then easier to see why different stops can affect key flavour, because timbre as well as the beat patterns are both strongly affected by the numbers and strengths of the harmonics in the sounds.
A consequential phenomenon is also discussed in which the subjective flavour of triads and other chords depends on how the composer constructed the harmony of a piece. In particular, the inversions in which the chords appear and whether they are written in close or open positions can result in marked changes in key flavour. This also is demonstrated with audio examples and explained as before in terms of beats and harmonics.
When unequal temperaments were more common than they are today, one can probably assume that composers would have deliberately wandered in and out of the less agreeable keys to add interest to their music. Moreover, it would not be surprising if they assumed that organists with sufficient familiarity would have learnt how to amplify or attenuate those effects by choosing their registration appropriately. Indeed, it would be more surprising if they did not, given that they would have come across the effects as part of their everyday experience. Perhaps most importantly, the article shows that keys which are routinely dismissed as 'intolerable' in the literature on temperament are not necessarily so on the organ, which has the ability to soften their effects because of the range of different timbres available.
The picture above is of a test rig used for experiments on pipe organ valves, such as those described in the articles entitled Calculating Pallet Size, Touch Relief in Mechanical Actions and Response Speed of Electric Actions. These can also be accessed from the Complete Articles page where summaries are also available.
This electronic organ is a dual purpose instrument containing both "straight" and "theatre" voices, designed and made by the author. It is tuned to the author's Dorset Temperament with the addition of some impure octaves as described in Keyboard Temperaments with Impure Octaves. A full specification can be downloaded here (PDF file, 717 kB).
The things they say:
These recordings span some years and they were made in various rooms and auditoria. The older tracks were made using analogue equipment and some were recorded acoustically using microphones, hence the occasional noises due to piston thuds and page turns, etc. Other tracks were captured electrically. All are of real players performing in real time - no synthetic MIDI 'performances' here. I have not got round yet to normalising the volume settings of all the tracks so they are compatible with each other, therefore you might wish to adjust the volume between tracks depending on which ones you select. Do not be alarmed if some tracks appear to start with an excessive noise level - this simply means they were recorded at a higher level than others. Just turn the volume down to suit. In any case, it is a wise precaution to always begin playing each track at a low level to protect your audio equipment and your ears from unexpectedly high signal levels when the music begins. Although the instrument has 13 ranks of theatre organ voices in addition to its 'straight' sounds (see specification), copyright considerations preclude the inclusion of much theatre-style music here. Playing time 1 hour 35 mins approx.