The concept and applications of a "virtual pipe organ (VPO)" are a 21st century development with which every organist these days needs to be familiar, whether they ever expect to use this type of instrument or not.
While, technically, this term is a misnomer since there are no pipes, a goodly number of churches, institutions, and individuals are moving these days to this type of instrument (and, considering their financial advantages over buying a digital organ outright, their splendid sound, and their ease of operation, they seem to be here to stay).
Hauptwerk is a computer program available from Milan Digital Audio designed to allow the playback or live performance of pipe organ music using MIDI (musical instrument digital interface) and recorded sound samples.
This technology was originally developed and launched in 2002 by Martin Dyde who, starting in 2006, continued to develop it as Crumhorn Labs, Inc.; Crumhorn Labs and Hauptwerk were acquired by Brett Milan of Milan Digital Audio in 2008.
The product takes its name from the German term for the Great manual of an organ (pronounced "howpt'-vairk).
Hauptwerk is an advanced computer organ system -- a VPO that takes full advantage of the enormous processing power of the latest high end computers to provide very complex pipe organ modeling and per-pipe sound shaping while maintaining the enormous polyphony necessary to model a pipe organ successfully; at its core it's a powerful and high performance specialist software sampler specifically designed and optimized for modeling pipe organs through the use of MIDI.
Hauptwerk software produces audio output signals through the computer's audio interfaces in response to input received from MIDI; this input may originate from an external MIDI keyboard, an electronic organ console with MIDI capability (just about all consoles built after 1980 are MIDI compatible), or from a MIDI sequencing program; the audio output is based on recorded samples which are then modified using several technologies.
Four versions of Hauptwerk have been released since 2002, the latest being in 2011; version 4 has a redesigned user interface, automatic facility to configure MIDI to support most manufacturers, an inbuilt recorder/player, user defined combinations/crescendos, and master couplers available with all organs.
Hauptwerk runs on Mac OS X and Microsoft Windows computers, and the organist's computer would need to meet the minimum requirements prior to downloading and installing Hauptwerk.
If we're buying a new computer to use with Hauptwerk some guidelines can be suggested, but Hauptwerk will still perform well with even quite moderately sized instruments (30 ranks or so) on older computers with just a single-core processor and all realism features enabled, provide that it has sufficient RAM (memory) for the virtual instrument the player wishes to use.
With the current version of Hauptwerk the minimum operating systems are Mac OS X 10.7 or Windows 7 (64-bit), with Mac OS X 10.11 or Windows 8.1/Windows 10 (64-bit) recommended.
The processor would need to be Intel 64-bit (preferably Quad-Core).
The computer would need a minimum of 2 Gb of RAM (memory), with 16+ Gb recommended.
There needs to be a minimum of 6 Gb of hard disk space for the core program, with 500+ Gb recommended for the program and instruments.
As to graphics, the minimum requirements are 1024x768 (16-bit color), with 1280x1024 (24-bit color) recommended.
Besides a computer and touch sensitive monitor screen, playing Hauptwerk live from several MIDI keyboards or a MIDI organ console will also require a MIDI interface and an external speaker system.
An evaluation version of Hauptwerk is available to test with candidate hardware before purchasing the program.
It's important to remember that computer technology evolves very rapidly, and the computing power that will be available in new computers is likely to double every 18-24 months (some refer to this as "Moore's Law").
The useful and working lifespan of computer hardware is typically only about 3-5 years; Hauptwerk owners should thus plan and budget for replacing their computer hardware accordingly; even when the computer still works in 5 years' time there's a good chance that the versions of the operating systems, hardware drivers, and applications that are current and available then won't be able to run on it; that's simply the nature of computer technology; it evolves very rapidly and becomes obsolete rapidly.
Computer hardware, operating systems, drivers, and software need to be kept reasonably up-to-date since they all depend on each other.
At any given time the most powerful computers available are usually much more expensive than computers that are only a little less powerful than them.
It thus often makes sense to buy computer hardware for Hauptwerk that's absolutely current (so that it takes advantage of the latest advances in technology and has the longest possible useful lifespan) that's reasonably high performance, but isn't the highest performance hardware available, then plan to replace it regularly (about every 3 years); this way the organist can remain fairly close to the "cutting edge" in terms of performance without excessive cost overall.
Computers also need some periodic maintenance too; operating system updates need to be applied, software applications need updating regularly, they need backing up regularly, and hardware needs checking and replacing periodically, so, it's important to plan and budget for such maintenance, replacement, and upgrades, both financially and in terms of ensuring that somebody with sufficient computer experience is available to perform it.