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Additive Organ Pipes

PostPosted: Sun Aug 20, 2017 6:15 pm
by HughBanton
Hi all,

Here at last is the current state of my additive-system pipe organ simulator - 'HB3' - which I started back in March. More to do but basically working OK now. Immediate thanks and acknowledgement for all the bits that I've 'borrowed' from others, and for one or two bits of vital help especially early on!

It's loosely based on the 1980s hardware 'Bradford Computing Organ System', which I used professionally in church organs for many years. Since it's demise a few years back I've wondered how it would translate into a PC-based version, so here we are. I've found It's been possible to refine and elaborate on the original concepts in every area.

What I've made produces a single organ stop, so to build an actual organ would need umpteen vst instances, in the same way that a pipe organ contains umpteen ranks of pipes, one for each stop, depending on its size.

I'm hoping it's sort-of self-explanatory, but essentially it has 6 'voicing points', one at each C on the keyboard, and it then interpolates between them to create harmonic levels for every keyboard note (well, actually 72 notes - there are 1/2-octave extensions at each end, to allow for transposition). It then writes 72 waveforms from this harmonic data, ranging in size from 1024 points for very low frequencies to 32 points at the top end.

Similarly there is an envelope generator for bottom C, and then a rate-scaling setting at each voicing point which is interpolated into 72 envelope speeds. (In general small organ pipes play faster than big ones). Also at each voicing point there are pitch modulation controls, noise/random modulation controls etc, all interpolated into 72 of each.

Four parallel sections, A,B,C & D (.. although I might lose one, haven't found a need for it yet) to separately create sustained sounds, attack & release elements and so on. You can view each section, turn them off, solo them etc.

One innovation I should mention: I've made myself an associated 'regulator' fsm, whose purpose is to write a table setting a level for every sine-wave semitone in the spectrum .. from bottom C at 16Hz up to top C at 16kHz, 10 octaves. This 'regulation table' is then referenced when the system is writing its 72 waveforms from all the harmonic levels, meaning that it can literally flatten (or manipulate), the frequency response of the combination of speaker & room acoustics. As far as I know this hasn't been done in a digital system before, but when you think about it ... it has always been possible on, say, a Hammond organ when the magnets adjacent to the spinning wheels were adjusted at the factory - which does the same thing!

I've loaded up 10 presets, examples of most families of organ stop.

Not done this before so I'm hoping the following works ..... ...

Hope it's of interest; looking forward to comments .. and advice!

Re: Additive Organ Pipes

PostPosted: Sun Aug 20, 2017 6:43 pm
by HughBanton
Well, I've not been able to open my own link! Try this one .. we'll get there eventually - ... 6.fsm?dl=0

Re: Additive Organ Pipes

PostPosted: Thu Aug 24, 2017 8:56 am
by Spogg
I’m really VERY impressed with this Hugh and many thanks for sharing such a huge and complex project. It must have taken a vast amount of hours to get to this point. The sounds are very convincing.

I would love to put this up on if you are in agreement and if it’s ready for release. If so, I would like a basic user guide to go with it because it seems to offer so many possibilities to tweak the many controls but, speaking for myself, I’m not sure what everything does and I’m not too familiar with organ terminology. Maybe you could include a link to a good background document if there is one you think is deserving.

Once again, well done!



Re: Additive Organ Pipes

PostPosted: Thu Aug 24, 2017 10:12 am
by HughBanton
Many thanks Spogg. You know how it is .. can't leave it alone once you get stuck into one of these! (And then there's the regular 3'oclock in the morning inspiration :idea: )

If you don't mind, best to keep it here and 'private' for the time being; for one thing, there were patents in force over some of this, and although they will likely have expired by now I really ought first to get back in touch with the original inventor (formally at Bradford Uni) to show him how I've been plagiarising his work!

Although I've only briefly got into 'voicing' it's clear that HB3 is going to be way more realistic than the original hardware was, I've been quite surprised at its 'sample like' quality. In some ways it's better - with the combination of sine-wave note regulation and universal interpolation I think I can claim near-perfect keyboard scaling.

Also yet more stuff to add, stuff to fix (.. isn't there always?); I'm having to contemplate how a typical organ console will interface, might be requesting some help on that.

I'm out for a couple of days; I'll come back with some pipe-organ terminology links and other info at the weekend.
Thanks again

Re: Additive Organ Pipes

PostPosted: Thu Aug 24, 2017 11:55 am
by Spogg
Yeah, tell me about the early morning thing! I sometimes wake at 4am for a wee (I'm 63 so it's expected I gather) then I can’t get to sleep again because I’ve come up with an idea for whatever is my current project. It’s all part of my Flowstone addiction I reckon. They should put up a warning on the website.

The patent angle is interesting. I made heavy use of Yamaha’s Formant Shaping USA patent for my Quilcom Informant. My FS version is an accurate emulation of their technique but of course it’s not done in hardware. I really don’t know if that matters but maybe it would be more relevant if I was selling the plugin. Something in me would quite like to get a Cease and Desist notice from Yamaha, just to print out and put on my wall.

While I was fiddling with your organ (I love saying that) my heart was crying out for reverb, to make it all Churchy. I’m not gonna suggest you provide one; just saying. If I make an organ preset for one of my synths I always add loads of reverb. Then I play the first bit of Toccata and Fugue in D minor, because I love it.

One thing I would ask about is the initial chiff of air noise. Is this modelled on the real thing? I can imagine hearing it if up real close to the pipes, but not at any normal listening distance. Just wondered.



P.S. This always makes me laugh...

Re: Additive Organ Pipes

PostPosted: Thu Aug 24, 2017 9:44 pm
by BobF
Hello HughBanton,

Wow, you have really showed what can be done with Flowstone here. I love this organ, a really great job. I do agree with Spogg though, it does need a Reverb and maybe some type of Resonant filter, or just a complete effects section. A Ring modulator would be nice for Bell tones. Look at some of Spoggs synths as an example of effects section. Sorry to rattle on, these are just suggestions, it's your vision . Hope to see lot's of really cool stuff from ya in the future.

Take care, BobF.....

Re: Additive Organ Pipes

PostPosted: Fri Aug 25, 2017 9:52 pm
by HughBanton
Thanks very much guys.
Just on the reverb thing .. HB3.fsm only simulates a single organ rank, intended to sound as it would if you stand in very close proximity to the pipes, inside an organ case. (Which is quite a surprising experience!)

So for a complete organ I'm envisaging multiple vst instances, i.e. lots of stops, played from a big console and mixed in stereo. I haven't got that far yet but once that's achieved you would add reverb and fx to the whole ensemble, rather than to the individual stops, if the natural acoustics (or studio requirements) demanded it.

But I appreciate that most people think pipe organs automatically all sound like Westminster Abbey! Unfortunately they don't - close up (even in Westminster Abbey) they all sound exactly like yer local village church ... it's true ;)

More anon.

Re: Additive Organ Pipes

PostPosted: Sat Aug 26, 2017 7:45 am
by Spogg
Makes good sense Hugh.

I once sat right in front of the Organ pipe cabinet thingy in Halesowen Parish Church (long since replaced with an electronic version)and was surprised at how kinda harsh and mechanical it sounded (and very loud!). I recall I could even hear the solenoids clacking away and what I believe must have been an air pump running. I then understood why these were the least popular pews. Elsewhere, especially at the back of the building, it sounded completely wonderful.

The organist, one long since departed Bertram Powell, would often give a brief organ recital after a service and I often used to stay back and listen in awe. When done well it’s a very moving experience.

When your project is complete I would love to hear some music pieces played on your system, even if it’s only from others’ MIDI files. A sonic demo goes a long way.



Re: Additive Organ Pipes

PostPosted: Sat Aug 26, 2017 1:51 pm
by BobF
Now I under stand completely, thanks. Can not wait to hear the final version. Great work!

Cheers, BobF.....

Re: Additive Organ Pipes

PostPosted: Sat Aug 26, 2017 8:46 pm
by HughBanton
Just the instant Pipe Organ Description that I promised ... (I figured quicker to write my own!). This is basically how it goes :

On a typical pipe organ console there are invariably two or more manuals (keyboards), and a pedalboard. Each manual operates its own personal wind-chest - that's a complicated matrix of a box, with multiple rows - ranks - of 61 pipes lined up on the top, one pipe for each keyboard note. A manual's wind-chest on a small organ may have 4 or 5 ranks of 61 pipes, a huge organ can have 20 or more - well over 1000 pipes per keyboard. On the console each stop knob belonging to a manual turns on one of the ranks when you pull it, by enabling the wind supply to the rank. This in fact is why they are called "stops" - plumbing!

This was all devised several hundred years ago btw.

So when you draw a stop it turns on a particular sound: a diapason, a flute, a reed etc. You can just pull one stop and play, but generally you draw more than one stop together. A manual plus its wind-chest is known as a Department.

Stops exist at different pitches, mostly octave related. Stops at 'piano pitch' are labelled "8-foot"(e.g. 'Open Diapason 8'), because 8' is roughly the length of the pipe that plays bottom C on the keyboard. A 4-foot stop plays an octave higher, 2-foot up another octave. There are a multitude of other pitches available, some of them fractional such as 2 2/3-foot, which for bottom C(1) plays note G2. Which happens to be the 3rd harmonic of C1, so rather than sounding discordant it blends in and adds colour. Here's another odd one .. 1 3/5', which plays E3; that's the 5th harmonic of C1. All sorts. You'll also find stops labelled "Mixture", which play several of these higher-harmonic ranks simultaneously, instantly recognisable as that brilliant sparkle that you get from an organ at full tilt.

So each department really is an independant organ. On a (British) two-manual organ the upper manual is called the Swell; it's wind chest & pipes reside inside a a soundproof box with heavy venetian-blind-like shutters on the front, opened and shut by a swell pedal on the console, much like a volume pedal. On the other hand the pipes of the lower manual, the 'Great', are open to the elements, but of course there are loud stops and there are quiet stops.

The decorative pipes you see on the front any pipe organ case are usually genuine by the way; they're the large bottom-octave pipes that don't conveniently fit anywhere on the wind-chests, so instead get pride of place at the front.

The Pedalboard has yet another set of stops all to itself, generally based an octave lower at 16', and again they have their own selection of colours and pitches, 16, 8, 4 & mixtures. Giant organs occasionally feature 32' stops - C1 plays way down at 16Hz.

Finally 'couplers'. So that the organist is not limited to the stops on a particular manual he/she can couple the departments together, so for example if the 'Swell to Great' coupler is drawn, and the organist play on the bottom manual, both Swell & Great play together in unison. Similarly Swell to Pedal couples the upper manual to the pedals. Drawing every stop and every coupler is, unsurprisingly, known as 'full-organ', although in practice an instrument performs rather better with some intelligent selection.

Now, all of this is utterly unlike the arrangement on that most ingeneous 1930s innovation the Hammond Organ - which may well be the subject of my next project HB4! (But I'll doubtless come back to that).

Hope this is of interest, and apologies to those who know all this stuff already :roll: