Sound fidelity is mainly understood to be a matter of sound generation and behavior. Characteristics of different pipes, their interaction with each other and the acoustics of the instrument’s surroundings are paramount to original pipe organ sound. An actual physical instrument is considered essential to authentic sound generation while acoustic features of the room can be technically simulated to some extent.
All starts with the individual pipe carrying indelible traces of both the pipe caster and the person voicing it. The so called transient is the phase where the air column oscillates at the labium or reed until it stabilizes to produce a homogeneous tone. Depending on the pipe’s overall measurements and especially those of its mouth, where the sound actually takes form, transients are different and influence the overall sound. Every pipe in its individual position is a sound source from which the vibrating air column is transmitted to the environment. In terms of interacting sound waves this means that the pipes ‘know’ and ‘talk’ to each other.
Another, often underestimated, sound source is the console itself. First, the oscillation build-up of a tone (transient) depends on the force used by the organist when hitting a key, which is in turn linked to the distinct key resistance of each organ. Second, the mechanisms running from key to tracker action to valves in the wind chest produce a distinct soundscape. So even before the pipe responds there is a lot going on in the organ, increasing the organist’s immediate connection to his instrument.
Equally important as the actual organ is the space in which it is situated. An organist pressing a key is first hit by the direct sound coming from the corresponding pipe after which the waves spread out until they hit the next wall from which they are reflected and again meet the organist’s ear. Reverberation depends on the surfaces and materials from which sound is reflected and on the signal’s frequency (in church buildings, low frequencies generally reverberate longer). A multitude of reflections create a diffuse sound field that fades with a specific, frequency dependent reverberation time. Although not entirely understood, such acoustic phenomena were known and taken into account by classical composers of organ music. The difference between direct sound and the diffuse sound field is usually only audible to the organist. For him it is particularly important that the room ‘carries’ the music because it allows taking the hands off the manual for a split second to change ranks without interrupting the musical experience.
Connected to this scientific understanding are more artistic claims and arguments centered on the immediacy of the organist’s connection to his instrument. Playing on a pipe organ with mechanical action engages the organist in a direct conversation with his instrument. He has an immediate connection between his fingers, the tracking action, the single valves, and even the coupling of manuals – all providing immediate feedback on his emotionally colored play. How an instrument reacts to the organist’s play, with resistance and delay, also has influence on tempo and caesurae: “Such feeling with the instrument is naturally impossible with a decoupled keyboard”.
In addition to this haptic experience, the fact that direct sound hits the organist from different sources around him evokes a feeling of sitting in the instrument, being enshrouded by music. This perception is usually amplified by the reverberation which depends on the room’s acoustic features and how they dampen and reflect sound waves. That sound is ‘being carried’ through a large room allows the “enjoyment of a cadence, when the room carries the chord after reducing key pressure, before the next chord sounds”. Being conscious of these factors the organist receives the continuous feedback necessary for his immediate connection to the events he controls from the console. In this sense, the instrument, the musician and the room form a musical symbiosis – a beautiful union of science, technology and art.
Notably, language presupposing the organ as complex living being is often encountered in the literature. This metaphor of the organ being alive, it seems, can be linked to the scientific arguments about sound generation. The complexity of this process, the changes over time and of the object itself as well as the long evolution of the tone until it slips into the inaudible spectrum apparently invite this view. A pipe organ needs air to function and slight variations in wind pressure have an effect on how the pipes ‘speak’, just like the human voice. Then there is the transient again, different for every pipe. Especially gedackt wooden pipes have a real life of their own until the tone is stable: they ‘cough’ a bit because wooden labia are not as sharp and the air column takes longer until it oscillates homogeneously. A sound’s antecedent is particularly distinct with low frequencies. An organ lives from reverberation in the sense that the sound pattern is not interrupted during the transition from one sound event to another. From the point where a key is hit until the tone stands clear and clean: “There’s life in it!”
All info on this page: P. Puschner (personal communication April 2015)
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