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Salisbury Willis Volume 1 Released

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Re: Salisbury Willis Volume 1 Released

Postby RichardW » Mon Mar 15, 2010 6:48 pm

one separate impulse response and convolver instance for each pipe.


What we need is some Cepstrum Analysis. Using that we could perform some homomorphic deconvolution on every sample in a sample set to separate the underlying waveform from its associated impulse response. That way without any more sampling you could have (theoretically) the basic building blocks you require.

This process relies on the facts that convolution in the time domain is the same process as multiplication in the frequency domain and that multiplication is like addition after you have taken logarithms. So deconvolution can be as easy as subtraction.

Then to replay the signal you could re-convolve all the waves with the correct IRs and get back what you started with. Oh, wait a minute, I think I have just thought of a quicker way of doing this ... :wink:

Below is the reference for the original paper on the subject for all those who think I have just made all this up (or flipped or both)!



B. P. Bogert, M. J. R. Healy, and J. W. Tukey: "The Quefrency Alanysis of Time Series for Echoes: Cepstrum, Pseudo Autocovariance, Cross-Cepstrum and Saphe Cracking". Proceedings of the Symposium on Time Series Analysis (M. Rosenblatt, Ed) Chapter 15, 209-243. New York: Wiley, 1963.


I hope this helps(!),
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Re: Salisbury Willis Volume 1 Released

Postby mdyde » Tue Mar 16, 2010 7:40 am

Hello Clive,

Perhaps I'm just splitting hairs here, but would there really need to be as many as literally one per pipe - eg not one per two pipes or one per four pipes, ... ? Still an awful lot of convolution reverbs to run at once, of course. But I was just wondering how coarsely spaced it would be possible to make the "grid" of IRs before it was possible to hear the difference from a one-per-pipe grid. I suppose we won't know til someone actually tries it?


Very slight differences in position can give significant differences in the pattern of early reflections (in an impulse response or wet sample) and the frequency response heard. For example the sound from one pipe might pass between other pipes on its direct path to the listener, whereas the sound from its neighbour might be reflected or refracted off another pipe or part of the case before it reaches the listener.

The subconscious brain is very good at detecting those slight differences in order to build up its spatial sound impression. E.g. if you close your eyes and play each pipe in a rank on a real pipe organ you can often tell its position with remarkable accuracy just from its sound as you play and release it, and relative to its neighbours.

That ability of the brain is largely responsible for allowing us to identify and hear each pipe separately within a real pipe organ, or within a wet sample set (or potentially a dry one with separate convolutions for every pipe), even if many pipes are sounding at once, giving perceived clarity.

If the same impulse response/reverb is applied to several dry pipes (or even all the pipes) then the brain is no longer so easily able to hear them as separate pipes/sound sources, and the result will lose perceived clarity.

It's exactly the same as playing a (dry) digital organ in a reverberant building - the more speakers you use, the better the spatial impression and clarity. Too few speakers and it can sound artificial and muddy. Each speaker equates to a separate convolver instance and impulse reponse when adding an acoustic virtually.

When I helped Brett with recording some of the original demos for the (dry) Virginia WuliTzer sample set using convolution and simple room modelling software to synthesize the IRs for a virtual theatre, we found that about 32 separate true stereo (2->4->2) IRs and convolution instances (64 standard stereo convolutions) gave a level of clarity and spatial impression for that 8-rank organ that began to sound fairly convincing to us. So that would equate to using about 32 speakers for a dry digital organ in a real reverberant room (four per rank on average).

The more speakers/IRs/convolvers, the better the spatial impression and perceived clarity. One for every two pipes would almost certainly sound extremely good indeed, but I suspect you would still be able to tell the difference in a blind test between that and one per pipe (which a wet set effectively achieves).

(There are other possible compromises, for example you could make a 'semi-dry' sample set that had only the early reflections within the samples, and then use a reverb unit or IR just to add the background wash of late reflections, which are less important to the brain in terms of spatial cues. That approach would have some of the advantages and some of the disadvantages of both wet and dry.)
Best regards,
Martin.

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Re: Salisbury Willis Volume 1 Released

Postby chorn » Tue Mar 16, 2010 8:47 am

^

Thanks, Martin. Very interesting to learn about your and Brett's experience with all those IRs required for realism with the WurliTzer.

I do seem to hear something "wrong" in some of the mp3 demos that have involved the addition of convolution reverb (on a far smaller scale): I can't quite put my finger on what's not right, though I think, sometimes, the reverb seems like it's not really part of the organ sound. By contrast, the mp3 demos from the wet sets mostly seem more real, some sounding stunningly real.

Hard to be certain, though - a danger of believeing you hear what you expect to hear - it would be interesting if someone did some proper testing of whether listeners can really distinguish wet samples from dry samples with convolution reverb added.
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Re: Salisbury Willis Volume 1 Released

Postby gingercat » Sun Mar 21, 2010 7:07 am

WOW! Just had my first play on the Willis and am grinning from ear to ear. What a presence this set has - you really get a feeling of the beast lurking behind the scenes when you play it. As for those doubting the merits of releasing in multiple volumes, well I challenge you to try this set and then complain you're not getting a full organ! Ok, it isn't the full Salisbury WIllis (obviously!) but it still contains enough colours to put most parish church organs to shame. The strings are just delicious! Congratulations to Brett and all those involved in producing this set (including a big thanks to the Cathedral for allowing the organ to be sampled).
Regards,
Chris Blaylock
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4 Manual Console, 32 R&C Pedalboard, 3xExpression, Solenoid coupler tabs
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Re: Salisbury Willis Volume 1 Released

Postby gingercat » Sun Mar 21, 2010 4:46 pm

I think there might be a couple of rogue tremulant samples on the solo Clarinet, particularly note 84 (think it is 84, C of octave 5) and then the D above that to a much lesser extent. The C in particular has quite a nasty beat to it which sticks out rather a lot.
Regards,
Chris Blaylock
i5 4670k, 32GB RAM, Win7, 2xELO 1280x1024 Touchscreens, Focusrite Saffire, MIDISport 4x4
4 Manual Console, 32 R&C Pedalboard, 3xExpression, Solenoid coupler tabs
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Re: Salisbury Willis Volume 1 Released

Postby DanielCook » Sun Mar 21, 2010 7:44 pm

Those notes sound exactly as they do on the real stop. In practice they are not really a problem.

Daniel
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Re: Salisbury Willis Volume 1 Released

Postby gingercat » Mon Mar 22, 2010 5:45 am

Thanks Daniel,
I had just assumed something had gone amiss with the sample set creation - should have known better than to expect a mistake like that from MDA! Just seems a shame to have such a beautiful stop which then suddenly sounds more like something on a detuned fairground organ for that particular note. I can only guess they don't cause a problem with the real stop by avoiding them wherever possible!
Chris.
Regards,
Chris Blaylock
i5 4670k, 32GB RAM, Win7, 2xELO 1280x1024 Touchscreens, Focusrite Saffire, MIDISport 4x4
4 Manual Console, 32 R&C Pedalboard, 3xExpression, Solenoid coupler tabs
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Re: Salisbury Willis Volume 1 Released

Postby toplayer2 » Mon Mar 22, 2010 6:53 am

gingercat wrote:Thanks Daniel,
I had just assumed something had gone amiss with the sample set creation - should have known better than to expect a mistake like that from MDA! Just seems a shame to have such a beautiful stop which then suddenly sounds more like something on a detuned fairground organ for that particular note. I can only guess they don't cause a problem with the real stop by avoiding them wherever possible!
Chris.

When using untremulated samples, the sound designer can easiliy transpose a neighboring pipe to replace one that is badly voiced. When using actual tremmed samples, transposition would noticeably raise or lower the oscillation frequency. Substituting an LFO treated note stands out like a sore thumb. Reed pipes in particular respond with a great deal of individuality to trem. One could view these peculiarities as charming and authentic.

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