Hauptwerk is a computer program, available from Milan Digital Audio, designed to allow the playback or live performance of pipe organ music using MIDI and recorded sound samples. The program is a commercial product but is available, with limited functionality, as freeware.

‘Hauptwerk’ is the German term for the great manual of an organ, from Haupt- (‘main’) and Werk (literally: ‘work’ or ‘opus’, here roughly ‘[power] plant’, ‘factory’, some place where something, a sound in this case, is produced). The German pronunciation of the word ‘Hauptwerk’ is [ˈhaʊ̯ptˌvɛʁk].


Hauptwerk was originally developed and launched in 2002 by Martin Dyde who, starting 2006, continued to develop it trading as Crumhorn Labs Ltd.

In September 2008 Crumhorn Labs and Hauptwerk were acquired by Brett Milan of Milan Digital Audio LLC.


Hauptwerk produces an audio signal in response to input received via MIDI. This input may originate from an external MIDI keyboard or from a MIDI sequencing program. An organ is constructed using a set of recorded sample files in conjunction with an XML configuration file that defines organ parameters such as ranks, stops, manuals, coupling and organ images for display in Hauptwerk's user interface.

The audio output is based on recorded samples which are then modified by several different technologies.

Sample playback

The recorded samples of the original pipes are divided into 3 main sections - start(attack), middle(sustain) and end(release or echo). When a note is played the attack sample is played followed by a loop of the sustain section. Start, end and release loop points are stored in the recorded sample file. When the note is released, the release or echo section of the sample is used, or specific release sample files can be defined for a note, or range of notes. This latter feature is useful in making the organ more realistic, for example the echo of a pipe after a short period will be different from that of a pipe that has been sounding for longer. Hauptwerk can select from multiple release samples based on the duration of the note. Tremulant effects are possible using LFO sample files to dynamically modify the sound, avoiding the need to create individual tremulant note sample files.

Harmonic filtering

When an organist moves an Expression pedal it affects both the volume and frequency envelope of the affected pipes. Hauptwerk adjusts both of these parameters using information provided within the sample-set. This can be based on measurements taken from the original instrument.

Physical modelling

The wind-pressure applied to an organ pipe affects its volume, pitch and character. Hauptwerk uses Fluid dynamics to model the movement of air through the various parts of a pipe-organ. This information is then used to modify the sampled sound.


Randomization is used to modify certain aspects of the audio output. The pitch of individual pipes can be randomly modified when a sample is loaded into memory. If multiple loop points are provided, in the sustain section of a sample, these are selected randomly. Additionally, Hauptwerk simulates some other effects, such as Wind Turbulence, using Randomization during playback.

Organ sample-sets

A picture of the organ at Bovenkerk, Kampen. One of the organs that has been recorded for Hauptwerk
One of the organs that has been recorded for use with Hauptwerk (Bovenkerk, Kampen)

Since the launch of Hauptwerk, a number of independent companies have recorded organs and made these available for use with Hauptwerk. By March 2009 more than 50 organs had been recorded. These include organs in many different countries including:

  • Bavokerk, Netherlands
  • Bovenkerk, Netherlands
  • Eglise de Saint Etienne, France
  • Palace of Arts (Budapest), Hungary
  • Salisbury Cathedral, UK
  • Stadtkirche Waltershausen, Germany

The majority of these organs have been detailed on a Google Map.

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