The Phoenix Organ System - How it works
The sound generation process in a Phoenix Organ uses the sample replay technique. One of the key issues in the control of an electronic organ is the allocation of sound resources. In a Phoenix Organ, a separate, independent generating source is used for each note of each rank in the same manner as a traditional (non extended, non unified) pipe organ. Some technologies in the market place do not work in this manner - sound generators are shared across stops. At Phoenix, we do not do this because we believe that it is important that an electronic organ replicates a pipe organ as closely as possible.
The basic building block within the organ is the Phoenix soundcard: the number of these will depend on the size and specification of the instrument. A Phoenix soundcard has 64 generators, each of which can replay one sample at a time. Each sound card has the option of software bass and treble controls on each of its four audio channel and when this option is implemented it reduces the number of generators by two per audio channel. If eight stops (ranks) are assigned to a single sound card without software bass and treble controls, then this will allow up to eight notes to be played with all stops drawn simultaneously.
The sound samples to be used by a soundcard are stored in memory located on the soundcard. Some of the samples for stops can be very large: this is because we use a large number of samples to cover the range of the stop, and each sample is quite long to ensure that the sound does not become boring. We therefore tend to limit the number of ranks (stops) on a sound card to about five, balancing the memory used by the samples and the polyphony of the soundcards (and hence the polyphony of the instrument).
We use high quality sound samples in our organs. The starting point for creating the samples we use is a digital recording of a pipe organ rank. We select a number of samples from the recording that characterise the sound of the rank across its key range. Then we make use of various software tools to adjust and correct these digital samples before incorporating them into our digital rank. Some digital ranks use up to forty or fifty long samples - virtually one per note. This is particularly important for flutes which contain complex and uneven starting transients (chiff) and ensures that these transients are naturally re-created from the original pipe itself. The use of multiple samples also avoids the "chromatic whistling" effect which seriously flaws the sound if too few samples are used.
Stop lists can, at times, be pretty meaningless, and we have all experienced the disappointment when the sound emanating from the organ does not match one's expectations from the engraving on the stop knob. This applies as much to pipe organs as electronic organs. At Phoenix, when we are building an organ we can select, in consultation with the customer, the appropriate digital ranks (samples) that match their requirements and aspirations. We are also able to make changes to the samples after the organ has been installed should this be required or desired.
When a Phoenix Organ is installed, our skilled staff will carry out fine regulation and voicing so that the instrument meets your expectations. Voicing is carried out using our own sophisticated voicing software. This gives us the added flexibility of being able to adjust the final sound of our samples on site to suit the space in which the organ is installed.
A pipe organ usually contains thousands of pipes. Each pipe can be voiced, regulated and tuned. Our system works on a similar basis. We can voice, regulate, adjust the attack and release, and tune every note of every rank independently. Our voicing software is Windows-based and easy to use - allowing the person regulating the organ to concentrate on the job-in -hand and not worry about how to use the software.
On a pipe organ, moving the expression pedal does not just vary the volume of the sound, it also changes the tone by damping higher frequencies. The Phoenix system software simulates this also, by attenuating these higher frequencies when the expression pedal is closed. The calibration curves of our expression can be set using the voicing software.
The effect of wind variation on a pipe organ can have a significant effect on the sounds we hear. Our system software simulates this effect, and using our voicing software, each stop's loading on the bellows can be set across three of the keyboard. A large Open Diapason's bottom octave will use far more wind than say the top octave of a Larigot. Each stopís response to bellows movement is also adjustable. Wind calculations are performed hundreds of times per second in the Phoenix control software to guarantee pipe-like response.
A pipe organ tremulant changes the pitch and loudness of a stop. We have incorporated this into our design, plus a feature to provide some randomness in tremulant levels which occurs in pipe reed stops. Our voicing software provides full tremulant adjustment.
One of the most important features in any organ is its response to key presses. The Phoenix Organ System utilises a scaleable multiple processor architecture for its main control system. For example, each keyboard is scanned by an individual micro-processor and key presses and releases are passed to the main organ control processor. This main control processor in turn controls the operation of the sound generation pre-processors, so controlling the sound of the instrument. Similar processors handle input from stops and pistons. More control processors are provided in larger instruments to ensure that the response to all events is always consistent and prompt.
The software for Phoenix organs has been developed using the Yourdon method. This is a modern structured analysis and design technique that is widely used in both business and computer control systems. Briefly, it involves the definition of the system requirements and then expands these into process tasks. By developing the control software using this formal method, the Phoenix Organ System software is much more likely to offer a reliable service than other systems.
An important feature of the Phoenix Organ System is the ability to configure the instruments on-site. Through our configuration software system it is possible to reassign functions to different controls.
The Phoenix Organ System can control wind blown ranks of organ pipes as well as digital ranks. Facilities are available within the control system for ranks of pipes to be attached to divisions of the organ and played through the console being managed by the Phoenix System. This enables the Phoenix System to be used to supplement an existing (or new) pipe organ by providing a new console system with up-to-date control facilities and some digital voices or for a principally digital Phoenix System to be supplemented by some ranks of real pipes.
© Phoenix Organs 2001-2005 Last updated 17th January 2005