Draw Bar Settings Handbook 44
The harmonic drawbars on a Hammond M-111 spinet organ.When Laurens Hammond introduced the Hammond electric organ to the world in 1934, he gave us an instrument with more control over the sound it produced than any other before it (and many since). The Hammond organ’s drawbars let the player control the nature of the sound at the level of individual harmonics, much like a painter can control the nature of colour by mixing a very few primary colours.This article is intended to clarify the function of the drawbars, and addresses such issues as (for example, how to combine 8′ and 4′ flutes with 8′ strings), and how to that most closely matches a particular instrument sound. A Brief Introduction to the Nature of SoundAny steady tone has three main attributes: volume, pitch, and timbre (pronounced “tamber”). The first two are pretty much self-explanatory, and won’t be discussed here. The third refers to the quality or character of the tone.
Prevention Services Clearinghouse Handbook of Standards and Procedures, version 1.0, OPRE Report # 2019-56, Washington, DC: Office of Planning, Research, and Evaluation, Administration. 44 6.2.2 Usual Care or Practice Settings. 44 6.2.3 Beyond the End of Treatment.
Two tones can be of the same volume and pitch but still sound radically different (imagine the same note played on a trumpet and a xylophone).There are several aspects to timbre, one of which is the distribution of harmonics in a tone. Most tones consist of a fundamental, together with several harmonics present in varying degrees. The frequency of the fundamental is what we usually perceive as the tone’s pitch. The purest tone consists of only a fundamental, and looks and sounds like this. A pure sine wave tone at 440Hz. Click to play.Harmonics are additional pure tones superimposed on the fundamental, each of which has a frequency that is an integer multiple of the fundamental.
Instead of hearing the harmonics as distinct tones, our ears and brain hear a tone of the fundamental frequency, but with a different character than the pure tone. For example, here is a tone with the same pitch as the sample above, but consisting of the fundamental with a bit of the third harmonic (3x the fundamental frequency) and a bit less of the fifth harmonic (5x the fundamental frequency) thrown in.
A more complex tone, still at 440Hz. Click to play.Notice that the tone still has the same pitch, but that the character of the sound is very different.The Hammond drawbars give the player control over the combination of fundamental and harmonic frequencies. There are nine drawbars for setting the levels of the fundamental and various harmonics and sub-harmonics (lower in frequency than the fundamental).Each drawbar has nine positions labelled from 0 to 8. Zero means off; the harmonic controlled by that drawbar will not appear in the generated tones.
The remaining positions will cause the specified harmonic to appear in varying amounts, with each increment producing about a 3dB increase.As a convenient shorthand, drawbar settings are usually written as a sequence of nine digits broken into groups of two, four, and three digits respectively. For example, a possible drawbar setting sounding like an 8′ Tibia stop is 00 8040 000.
Drawbar Settings as (Pipe Organ) StopsThe individual drawbars are believed by some to be the equivalent of stops on a pipe organ, but they should not be seen this way. When an organist selects a single stop on a pipe organ, the resulting tone will be a complex one with many harmonics.
The complexity of the tone depends on the type and number of ranks of pipes that the stop controls. A stop controlling a single rank of flute pipe will produce almost pure tones, whereas one controlling two ranks of diapason pipes will produce tones rich in harmonics.Hammond drawbars on the other hand select individual harmonics. Usually several drawbars must be pulled varying amounts to achieve the effect of an individual stop.For any given stop found on a typical church or theatre pipe organ, there will be a drawbar setting that approximates the sound of that stop on a Hammond organ. Spectrum of a 440Hz tone with registration 00 8767 054The peaks and their amplitudes are: FrequencyHarmonicAmplitudeRelativeAmplitudeDrawbarSetting440 HzFundamental4dB0dB8880 Hz2nd1dB-3dB71320 Hz3rd-2dB-6dB61760 Hz4th1dB-3dB72200 Hz5th-88dB-92dB02640 Hz6th-5dB-9dB53520 Hz8th-8dB-12dB4If we now arbitrarily equate 0dB to a drawbar setting of 8, then every 3dB down from that corresponds to one drawbar increment down (anything -24dB or below becomes zero). One can see that the frequency spectrum of the tone corresponds exactly to the drawbar setting that produced it.One can take advantage of this to derive a drawbar setting for an arbitrary tone. Starting with a recorded sample of the tone, use a tool like Audacity to generate a spectrum analysis, and write down the intensity of each peak. Equate the highest intensity to a setting of 8 and determine the settings of the remaining drawbars relative to that, so that each 3dB down from the highest corresponds to one drawbar increment down.This technique works for almost any steady tone that one can get a recording of.
For example, I found this of a female vocalist singing melisma style. Here is the frequency spectrum from the second G# note in the performance.
Spectrum of a female vocalist singing G# melisma style.The peaks and their amplitudes, and the corresponding drawbar settings, are: FrequencyHarmonicAmplitudeRelativeAmplitudeDrawbarSetting415 HzFundamental9dB-2dB7831 Hz2nd11dB0dB81246 Hz3rd0dB-11dB41661 Hz4th-5dB-16dB32077 Hz5th-19dB-30dB02492 Hz6th-31dB-42dB03322 Hz8th-18dB-29dB0The drawbar setting to match this singer’s voice as closely as possible is thus 00 7843 000. Here is a clip of the aforementioned G# as sung by the vocalist, followed by the same note played with this drawbar setting. One second of a vocal G#, followed by one second on the Hammond. Click to play.The graphic above shows both the singer’s waveform ( blue), and the Hammond’s ( red). The shapes aren’t exactly the same because the phase relationship between the harmonics isn’t the same, but research has shown that our hearing is insensitive to phase relationship. Also notice that in the singer’s waveform, there are additional small “jaggies”. These are from the higher harmonics that the Hammond cannot produce.Here is another spectrum plot, comparing the spectra of the vocalist with that of the Hammond imitation.
The purple areas are where the spectra coincide. Notice that all the higher harmonics are missing from the Hammond tone, as is all the non-harmonic content of the actual singer’s voice. Comparative spectrum of vocalist (blue) and Hammond (red). Hammond ShortcomingsAlthough a Hammond organ can reproduce many pipe organ stops, pipe organ registrations, and arbitrary sounds quite well, it falls short in some respects. Some of the shortcomings are:.If you create a drawbar setting for a pipe organ stop, it can often sound very much like the real thing. But if you create a setting for a combination of stops (a registration), it may not sound as full as the actual organ.
When multiple ranks of pipes play at once, they will never be perfectly in tune with one another. On the Hammond however, the harmonics for all the stops are being produced by the same tonewheels, so it will sound as if the pipes were exactly in tune. The result might be too perfect to sound realistic.The Hammond drawbars only give you up to the 8th harmonic, omitting the 7th. Sounds that contain significant portions of 7th harmonic or harmonics beyond the 8th will be lacking when reproduced on the Hammond. Additional harmonics are available on some models. For example, the spinet models provide a combined 10th/12th harmonic drawbar on the lower manual, and the H-100 series provide both 7th/9th and 10th/12th drawbars.When more than one note is played, the same tonewheel might be contributing different harmonics to different notes. In theory, that tonewheel’s contribution will sound proportionally louder, but in practice, it will not be quite as loud as expected due to resistive losses in the magnetic pickup.There’s more to timbre than the character of the tone.
Drawbar Settings Handbook 44 1
The envelope is also important. For example, a Hammond organ can be set to play approximately the same harmonics as a piano, but it will never sound like a piano. Piano notes have a sudden but not instantaneous attack followed by a gradual decay. Hammond notes have a nearly instantaneous attack (complete with key click), followed by steady volume, followed by an instantaneous decay.ReferencesDictionary of Hammond Organ Stops – A Translation of Pipe Organ Stops Into Hammond-Organ Number Arrangements, by Stevens Irwin, 1939, 1952, 1961, and 1970.A Primer of Organ Registration, by Gordon Balch Nevin, 1920.
A copy of this book is available., by John Savard, 2010, 2012. This page goes into the workings of Hammond tonewheels in great detail, and is highly recommended reading for the technically inclined Hammond enthusiast.Related ArticlesIf you've found this article useful, you may also be interested in:. BillMay 21, 2009A college professor said timbre was determined by the relative strength of harmonic or non-harmonic overtones. The transient (chaff), happening at the beginning of the sound, is also an aural identifier, as well as the amplitude envelope of a sound (ADSR). It 'sounds' like the Hammond does a pretty good job of approximating the steady-state regime of oscillation within a sustained tone.The proper balance of the drawbars reminds me of an experiment I did producing strong heterodyne frequencies on the electric guitar. I added distortion to create strong overtones (h1,h3,h5for a square-wave), then fed the sound of two strings playing together, in a close interval, through a variable band pass filter (wah). When the wah was tilted back or forward into the right spot, the amplitudes of the two strings were adjusted to a relative level which produced a very strong difference tone.
John SavardMarch 04, 2011This is indeed the mathematically sound way to combine drawbar settings. However, I think it needs just one minor change. When the sum goes over 181, instead of dividing by the largest value and multiplying by 181, it would be better to multiply by 128. That way, “8” will be an accurate fit to the loudest component of the registration, instead of being too low by the maximum allowed error. (Of course, one could look for an overall “best fit”, but that’s more complicated.).
RayJanuary 16, 2016Fascinating article, Stefan. Thank you very much.I’m trying to understand the math concerning how much volume comes out of a single tone wheel depending on keys played and the current drawbar setting.Let’s say that my drawbars are set to 008800000 and I play a C. I understand that it will sound on two tone wheels. But what happens when I play a C and the C an octave above it? 3 tone wheels are required one one of them will be used by both notes. How does that change the volume coming from that tone wheel? Is it doubled?
And then, how does that scale up as more and keys (and drawbars) ask for more from that tone wheel?And what happens when using a setting like 008400000 where both notes use the same tone wheel again but one wants the volume at full and the other at half? Does the louder volume win? Or is it something 1.5x louder?Thanks again!. Stefan VorkoetterJanuary 16, 2016Ray, the short answer is that there is no simple answer. The resulting volume (in the “88” case) will be more than just 1x the single-key volume, but less than 2x the single key volume. The generator for each tone has a resistance inherent to the coil. The generators are also connected to the keys via resistance wires.
So to figure out the volume from a given tonewheel that finally makes it to the amplifier requires that you calculate the current flowing through each path. In the case of two keys using the tonewheel at once, the resistance of the coil is common to both paths, but then the current splits and flows through two different resistance wires to the keys, and from there into the mixing transformer (which also has an inherent resistance). If the two drawbars involved are not both set to the same amount, then the two tones flow into different taps of the transformer, and thus see a different resistance in the transformer. On the console Hammonds, this is further complicated by the resistance wires not all having the same resistance (this is known as tapering), so it depends on which two keys you play as well. It is of course possible to calculate what the volume from a given tonewheel will be in any given case, but it would be rather time consuming to do so. Stefan VorkoetterJanuary 17, 2016Well, doing what you suggest, and if you were mathematically inclined, you’d end up with a set of simultaneous equations that you can solve to determine what’s actually going on.
Nist Handbook 44 Tolerances
Of course the other way to do it is to measure the generator impedances, look up the values of the resistance wires (there are table in various places on-line), and measure the mixing transformer impedances. Then you’d know exactly what’s happening. Are you trying to develop a clonewheel? Hardware or software?. RayJanuary 17, 2016Yes, I’m working on a software clone and at the moment, this is my biggest question mark (among many otherslol).
At this point, my best guess is that each note on adds somewhere between 0 and 1x more output to any tonewheel (scaled by the drawbar setting which is non-linear as well), although it seems doubtful that it’s a linear doubling. One thing I’ve noticed is that if you play a large number of keys on a real Hammond, it doesn’t seem proportionally louder, but bad clone wheels are proportionally louder, so there’s some kind of natural compression going on in the real machine, and I’m pretty sure that this (unknown) algorithm is at the heart of it. Thanks for your input. Feel free to email me off list. Stefan VorkoetterAugust 19, 2016If we’re only talking about Hammond organs, then there’s a world of difference. For one thing, direct analog keying causes keyclick, as notes are switched on an off in mid-cycle.
Secondly, the various harmonics don’t all turn on an off simultaneously, since there’s a separate key-contact for each one, and their relative alignment is never perfect. If you push down a Hammond key very slowly, with all the drawbars pulled out, you will hear each harmonic enter the mix at a different time. Likewise, when you release the key, the harmonics each stop sounding at slightly different times. A good player (not me) can use this to affect the attack and release characteristics of the sound; press the key quickly and the note starts crisply, press it slowly and it starts with a chirp. Yes, I suppose you could fake all that with a velocity sensitive MIDI keyboard and a sufficiently accurate simulation of a tonewheel generator, but I’m not sure anyone does.
Then of course there’s the MIDI latency, which direct analog keying does not suffer from. Steven VienMay 04, 2017Stefan: I just bought a ’70s C 3 and Leslie 122 and I’m looking for the combination of stop bars that will give me the ’70s progressive rock nasty grind heard on records like “the Yes Album”, ELP’s Tarkus, Quatermass, etc., and I’m too old to screw around looking for that combination, assuming I have the equipment necessary to get there. If a larger amplifier is needed with some distortion, l have quite a few ’70’s guitar amplifiers that I can distort by turning them up or adding gain, if necessary, but I was hoping that tone could be recreated with the organ and the 122, as I’d like to seep the volume down if possible. Do you know what sound I’m talking about, and is it possible. Either way, you deserve a cup of coffee on me.Thanks, Steve Vien. Lars HamreMay 05, 2017It’s easy to determine what the values are as long as you have some kind of level meter that shows dB (rms/peak/analog/digital isn’t important). Pull out a single drawbar, then go through the steps and note down the values.
You could even do it on the frequency spectrum graph you show on this page, if it’s possible to zoom in a bit closer.How all those people have managed to come up with those methods but not actually measured the values is odd 🙂Maybe all the steps are closer to 3 dB in models where the drawbars use resistors to change the level (like the L100), instead of the matching transformer windings (A100, B3, etc), but those are not the popular models, and I have never measured them.I use the values above in Viscount Legend, although converted to a smooth drawbar curve and not 8 steps. Edward GrabczewskiMarch 18, 2018This is a very complete, comprehensive and satisfying article on the relationship of drawbars to real spectra. You’ve managed to put into words what I sensed about the way these things should be understood. I’m also grateful for clarifying the debate about Steven Irwin’s registration combinations. Maurice Grudin in “The Well Timbred Hammond Organ” also had a technique for combining stops but it’s good to know that Porter Heaps, an experienced organist, came closest to your system, with a methodology that’s simpler to apply than the mathematics of your own system.
More of a rule of thumb for those in the field. Disclaimer: Although every effort has beenmade to ensure accuracy and reliability, the information on this webpage is presented without warranty of any kind, and Stefan Vorkoetterassumes no liability for direct or consequential damages caused by itsuse. It is up to you, the reader, to determine the suitability of, andassume responsibility for, the use of this information. Links toAmazon.com merchandise are provided in association with Amazon.com.Links to eBay searches are provided in association with the eBaypartner network.Copyright: All materials on this web site, including thetext, images, and mark-up, are Copyright © 2019 by Stefan Vorkoetter unless otherwise noted. All rights reserved.Unauthorized duplication prohibited. You may link to this siteor pages within it, but you may not link directly to images onthis site, and you may not copy any material from this site toanother web site or other publication without express writtenpermission.
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