Virtual Pipe Organ Basics - How it works
Virtual pipe organs are different from digital pipe organs in many ways, but most importantly, in the amount of data they store. Recent digital pipe organs may be similar, but many of them already in use store about a thousand times less audio data than software organs can host. For example, a large organ with all pipes recorded in high-definition audio quality takes up about 50,000 MB of data whereas a typical digital organ stores about 256 MB. You can imagine how different the sound quality will be.
Virtual pipe organs work using a computer, specific software and a multitude of sound sample data. All of these are connected to a physical console or keyboard that you play, which controls the software using a standardized control protocol called MIDI, and the computer produces sound via a sound module and loudspeakers or headphones. This system is made of elements available both in parts as consumer electronics or embedded by certain manufacturers called virtual pipe organ builders.
Software and content: sampler platform and sample sets
A core part of the virtual pipe organ is the software, which is often a sampler platform that can recognize and play back the sounds provided in data banks, sample sets or sample libraries - all meaning the same. The term ‘sample’ stands both for the recording method and the data obtained.
The capabilities of the software will have a large impact on the features you can expect from a virtual pipe organ, but if the software platform is generic enough, it is often the sample library or sample sets that make the difference in terms of features.
There are several virtual pipe organ platforms, among them Hauptwerk. Inspired Acoustics sample sets for Hauptwerk implement various features of the real organs that are unique to IA sample sets.
Hardware and interface: computer and MIDI organ console
The role of the computer in a virtual pipe organ system is to run the software that works on producing the sound using the sample library. There needs to be a human-computer interface added to the system so that you can play on it: this can be a regular MIDI keyboard or an organ console. MIDI is a standard protocol for music devices that interconnects them and delivers messages in real time, for example, when you press a key or change a stop. These messages are control messages only, and contain nothing else than the information on which key was pressed and when. The computer software continuously listens to these messages and plays back the required sounds in real time by using the sample libraries. The latency (delay) of these systems can be unnoticeably low so that you can actually perform on the real organ sounds, in real time.
MIDI compatible organ consoles are available on sale both new and used, or can be custom-made by various vendors tailored to your functional and aesthetic needs.
Sound systems and installation
The last, and perhaps the most easily overlooked part of reproducing the sound of a pipe organ is the sound system itself. Sound systems can consist of two or more loudspeakers, one or more subwoofers, arrays of loudspeakers or, simply, headphones.
Depending on where you install your loudspeaker system, to authentically reproduce a virtual pipe organ, the system needs to be large and good quality enough to deliver the sound pressure level of a real pipe organ with minimum distortion. Since pipe organs drive loudspeakers into their most exhausting working conditions, before making a purchase it is advisable to consult a professional to find suitable systems without overdriving them. In many cases, if you can use multiple speakers, you may get better sound, resembling a real pipe organ experience.
If you install your virtual pipe organ in a less reverberant or dry environment, such as at home or in smaller volume or highly damped spaces, it is recommended to use a sample set recorded with reverberation (wet or semi-dry sample set) or use additional reverberation to make the recording sound better. In many cases, practicing can be more successful if the sound is less reverberant, as then the reverberation will not cover the nuances of the music texture. On the other hand, impressing your friends with a large cathedral sound does require larger reverberation.
Installing virtual pipe organs in a reverberant environment is also possible. Depending on the volume and properties of the space, a semi-dry or dry sample set may work best. Voicing the organ to match the sound system and the acoustic space is also often a necessity. This is a one-time process that is usually done by professionals who install the virtual pipe organ system in your church or institution.
The sound quality of virtual pipe organs is determined by a multitude of factors, and among those, the weakest element will determine the final quality perceived.
The sound quality is first determined by the sample set itself, how it was recorded and how it was processed, and, of course, how the original instrument was working at the time it was recorded. If the pipe organ was in a good condition or it is a well-maintained instrument, chances are high that you get a good virtual pipe organ out of it, assuming the developer has the right tools and methods in place and made good aesthetic decisions during the recording, on where to place the microphones, etc. If the organ is not in a good condition or it is not well-built or maintained, post-processing can help a lot, but Inspired Acoustics places high importance on authenticity, therefore avoids over-engineering.
Loudspeaker systems and their installation also greatly affect the perceived quality. An adequately large and wide-frequency range system is required. If the organ is installed in a dry space and you wish to add more reverberation, it is often the case that loudspeakers mounted not just near the hypothetical organ position but everywhere else around you would deliver a more convincing experience.