Sampled VS Physical Modelling For Organ Stops

Viscount Chorum 60 – Four Major Schools Of Organ Building

Can a computer really produce an authentic pipe sound?

Of course, nothing equals the sound produced by windblown pipes IF:

  1. The organ has sufficient stops
  2. The pipework was properly voiced
  3. The room has proper acoustics to support an organ
  4. The builder can design one instrument that can play music written over a 800 year period

That’s a tall order!

Just because an organ was built with real pipes doesn’t mean it’s a “good” organ. Over time, instruments can deteriorate from poor maintenance or changes to the physical space. Many organs end up in rooms that are “dead” and have no proper reverberation, or stuck in the wrong place in the room because no other space was available. Often, the initial organ was built as a compromise based on a budget, and the instrument simply doesn’t do an adequate job of supporting the literature – the congregational singing – or the choir.

Few instruments have even existed for as long as the pipe organ has. Dating back 300 years before Christ, the organ has a rich history as the first attempt to synthesize the voice of man. Until the invention of the printing press in the 1400’s, the early music written for the instrument was lost. Since then, organists have produced music for players and singers – and of course organ students. A modern organ is required to “play” all of these different styles of organ music. That’s a huge task for one organ!

Since the 1970’s, digital organs have tried with ever-increasing success to reproduce the sound of real windblown pipes. The computer technology to accomplish this has vastly improved until organs can be built today that rival the sound of a pipe organ. Two methods continue to evolve to achieve this.

Sampling – recording the sound made by a pipe and then playing it back

Physical Modelling – using computer algorithms to calculate the sound waves created by a pipe

Each of these methods has its uses depending upon what the listener wants the organ to sound like.

Sampling Technology

In the case of sampling, whole organs can be recorded and stored for playback on any instrument. The best pipe organs in the world become available to anyone, anywhere.

For sampling to be the most effective, every single pipe in the organ must be recorded note by note. Then, the samples are painstakingly processed to ensure that each note is in perfect tune and that the speech of the note has no defects. In this way, each rank of pipes in the organ can be played back from the organ console. The only limitation is the hard-drive space it takes to store all of the samples and the huge amounts of RAM to store them during a performance.

It is also possible to record each pipe from multiple locations in the room so that the acoustics of the location can be retained in the finished sound. This is not as critical today as the computers can digitally add room acoustics to the sound so that the user can select the “size” of the room desired. A living room can become a cathedral, if that is the type of environment the organist wishes to play in. Many organists are thrilled to be able to change the room’s acoustics as they practice or perform the breadth of organ literature.

In a sampled organ, the sound recording for each note is loaded and played back as the organist presses down a key on the console. Even if all the stops (voices) of the organ are selected, the computer loads each note’s recording and plays them until the key is released.

Physical Modelling

The first digital organs in the 1970’s used computers to generate pipe organ sounds using complex mathematical calculations to reproduce the sound waves created by wind blowing in a pipe. The same computers used to calculate the landing trajectory for the Lunar Module were modified to create the complex math equations that model a pipe.

Physical modelling takes more computer processing power, but little storage space since the sound is created “on the fly” as each key is pressed on the organ console. The software in the system can be used to program the model in many ways until the exact sound desired is produced. This is much like the “voicer” from the organ builder’s shop coming to the church and adjusting each note of each pipe until the best sound is heard.

But with an organ such as the Viscount Physis® , it is easy to select from a growing library of over 1000 pipe models to build custom organs in just a few minutes. And ranks can be tweaked easily to accommodate specific organ works. The new organ setup can be stored by the user in a memory location and then recalled at will. The flexibility is endless!

Viscount Physis® Organ Technology

Both of these technologies have strengths and weaknesses. But both of them have several important advantages that have to be considered:

  1. Cost – on a “per rank” basis, the initial cost for a digital organ is around 25% of the cost for a pipe organ. The digital organ requires virtually no maintenance, so the cost of ownership over time declines.
  2. Maintenance – A pipe organ has to be regularly tuned and maintained just like any other machine. A digital organ will always stay in tune no matter what the weather is doing.
  3. Space – a pipe organ requires a lot of space, not only for the pipework, but also the blowers and wind chests. Tuning problems abound when parts of the organ are at different levels in a building and the air temperature and humidity changes. And pipes need to be placed where the choir is located so that the volumes can be properly balanced, and the listener hears both from the same place.
  4. Upgrades – Pipe organs tend to remain very “fixed” as it is difficult and very expensive to make even a small change to their sound. The Viscount organs can up changed and upgraded by either the user or the dealer at any time. New pipe rank models are made available each year so that the organ’s flexibility will to continue to grow over time.