|
|
|
Last updated: 30 January 2012. Click About This Website for update list. ●● This site is now mirrored at www.colinpykett.org.uk (more >>) ●●
For over twelve years the most stable and extensive reference source on the Internet for pipe and electronic organs
The hub of this site is the Complete Articles page which gives you instant access to many detailed articles dealing with numerous technical aspects of both pipe and electronic organs. Use the Google search box below to quickly identify areas of interest. While browsing, why not also listen to over three hours of music played on the three manual organ below and the Prog Organ virtual pipe organ here?
!! NEW ARTICLE !! - Signals, Noise and Bit Depth in Virtual Pipe Organs
This
article discusses two issues which arise when preparing waveform sample sets
for virtual pipe organs: the recording bit depth and how to remove noise from them.
The dynamic range of organ pipes extends
from that with the greatest SPL to the weakest harmonic of that with the smallest. An example
is given of an
organ whose dynamic range lies within 16 bits but without much
of a safety margin. Therefore it is suggested that at least 20 bits would be a realistic working
minimum, though this could be reduced by judiciously varying the gain to match
the level of the sample being recorded. Noise on the samples is dominated by the organ
blower. Three ways of reducing it are high and low pass filtering to reduce outband
noise, conventional subtractive noise reduction, and the
application of VPO-specific tools. A
custom tracking comb filter is described which capitalises on the different power distributions of noise and
signal as a function of frequency - noise exists at all frequencies across a
significant part of the audio spectrum whereas the wanted signals have their
power confined to well defined harmonics. This
difference enables the amplitude and frequency of each harmonic or partial to be
tracked automatically from the start of the attack transient of the sound, through the sustain phase
and then to the end of the release transient including room ambience.
Because power at all other frequencies is ignored, the result is
completely noise free.
SEARCH THIS SITE
The picture above is of a test rig used for experiments on pipe organ valves, such as those described in the articles entitled Calculating Pallet Size, Touch Relief in Mechanical Actions and Response Speed of Electric Actions. These can also be accessed from the Complete Articles page where summaries are also available.
Pictured above is an experimental digital organ which simulates many different pipe organs (Prog Organ). Also see the article entitled Re-creating Vanished Organs.
This electronic organ is a dual purpose instrument containing both "straight" and "theatre" voices, designed and made by the author. It is tuned to the author's Dorset Temperament with the addition of some impure octaves as described in Keyboard Temperaments with Impure Octaves. A full specification is available here.
The things they say:
Hear it: (These recordings span some years and some tracks were made using analogue equipment. I have not got round yet to normalising the volume settings of all the tracks so they are compatible with each other, therefore you might wish to adjust the volume between tracks depending on which ones you select. Do not be alarmed if some tracks appear to start with an excessive noise level - this simply means they were recorded at a higher level than others. Just turn the volume down to suit. In any case, it is a wise precaution to always begin playing each track at a low level to protect your audio equipment and your ears from unexpectedly high signal levels when the music begins. Although the instrument has 13 ranks of theatre organ voices in addition to its 'straight' sounds (see specification), copyright considerations preclude the inclusion of theatre-style music here. Playing time 1 hour 25 mins approx).
Website copyright © C E Pykett 1999-2012. See About this Website.
|
