Moog String Filter

DSP, Plug-in and Host development discussion.
JCJR
KVRAF
2352 posts since 17 Apr, 2005 from S.E. TN

Post Sun Mar 27, 2016 11:54 am

That scientific american article I earlier mentioned-- Was long ago and I confabulated the date of publication. Recalled it in the 1970's, but this appears to be the article in 1981. There was another article "The Physics of the Violin" but that was 1961. If I read the 1961 article, I don't recall it. -- http://www.scientificamerican.com/artic ... in-plates/

Hmm, both SA articles were by Carleen Maley Hutchins and apparently those are the only two SA articles she wrote, 20 years apart. Wonder if she is somehow related to brilliant Bernie Hutchins of electronotes fame? Google shows no results for the combination of names. She has a wikipedia entry-- https://en.wikipedia.org/wiki/Carleen_Hutchins Apparently a famous violin builder/designer/researcher!

Here is the article-- http://fiddlerman.com/wp-content/forum- ... plates.pdf

Would suppose that there is more recent research on the topic. In that 1981 article, though all the content is interesting, the resonances and method of measurement is displayed on page 10--
The curves reflect the same test procedure: a constant-current sine wave to the bridge, with the response of the violin (hung on rubber bands) picked up by a microphone 14 inches away in a fairly non-reverberant room.
So perhaps rather than taking violin/viola/cello/bass violin audio recordings and trying to infer the resonances, it might be more "accurate" to locate excellent examples of the instruments, unstring them (or somehow non-destructively mute the strings, lots of twine or foam wound in the strings or whatever). Then test with a method at least as good as those used by Ms Hutchins. Or find good academic papers somewhere, where such careful measurements have already been published.

Am wildly guessing an unstrung instrument would give better measurements. Could perhaps get decent-enough results out of something like Room EQ Wizard, given proper measuring equipment and room. Dunno if strings could be sufficiently muted without messing up the body resonances. The muted strings would perhaps drain too much energy out of the resonating body. OTOH, without string pressure on the bridge, perhaps the "un-strung" body resonances could have different frequencies and amplitudes compared to the instrument strung-up in playable condition?

Alternately, maybe the resonances could be measured by recording a large series of recorded violin notes, then process the many notes to eliminate the pitch-specific harmonics, resulting in the body resonances common to all notes? Maybe a scale played pizzicato would be better than a scale played with the bow? The body resonance might also have different characteristics when held in playing position, and perhaps the body resonances could even vary according to which player is playing the instrument? How the player holds the instrument, etc.

The sample recordings ideally would be done in a very dry quiet room. Maybe anechoic chamber most ideal? Most rooms contribute significant resonances to any recording. Would be a shame to be trying to emulate accidentally recorded room resonances, when you thought you were copying the instrument body resonances! :)

Edit-- The chart in that electromusic article appears the same as one of Hutchins' measurements posted in the 1981 SA article.

Leslie Sanford
KVRAF
1597 posts since 4 Dec, 2006

Re: Moog String Filter

Post Sun Mar 27, 2016 1:33 pm

JCJR wrote:So perhaps rather than taking violin/viola/cello/bass violin audio recordings and trying to infer the resonances, it might be more "accurate" to locate excellent examples of the instruments, unstring them (or somehow non-destructively mute the strings, lots of twine or foam wound in the strings or whatever). Then test with a method at least as good as those used by Ms Hutchins. Or find good academic papers somewhere, where such careful measurements have already been published.
Hi JCJR, thanks for the link to the article.

I've done some experimenting with impulse responses from string instruments with some pretty good results. Unfortunately, good instrument impulse responses seem to be very rare. However, in doing my research, I ran across this device:

http://signalwizardsystems.com/vsound.html

It's meant for use with electric violins; it convolves the impulse response of an acoustic violin with the output of an electric violin to impart a realistic sound.

Examples:

http://signalwizardsystems.com/vsound.html#Downloads_vs

I'd love to run a synth violin patch through this device but can't justify spending the money on it at the moment.

They provide free software to use with the device. Included in the download are the impulse responses of several violins. It's pretty interesting looking at their frequency responses. I've adapted the impulse response for use with SIR2, but it just doesn't sound as good as their examples.

Leslie Sanford
KVRAF
1597 posts since 4 Dec, 2006

Re: Moog String Filter

Post Sun Mar 27, 2016 4:10 pm

A test running the Tetra synth through a convolution reverb using an impulse response from a cello.

http://www.lesliesanford.com/music/temp ... st-002.mp3

Apologies for the chime you hear every few seconds. I'm using the demo version of SIR2 (hope to purchase it soon).

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Chris-S
KVRAF
2605 posts since 10 Nov, 2013 from Germany

Re: Moog String Filter

Post Mon Mar 28, 2016 6:28 am

Convolution works very well. So what is the benefit for a special string filter?
More flexibility?

Leslie Sanford
KVRAF
1597 posts since 4 Dec, 2006

Re: Moog String Filter

Post Mon Mar 28, 2016 7:08 am

Chris-S wrote:Convolution works very well. So what is the benefit for a special string filter?
More flexibility?
There's the geek factor of just thinking it's cool to know how to use filters to achieve comparable results. Say you figure out a combination of comb filters that do the trick. You then have 'portable' knowledge you can apply to a variety of platforms.

But in the end, it does come down to flexibility. Decent instrument impulse responses are exceedingly rare; I've only found one cello IR I like. Imagine having a convolution reverb with only one IR of a concert hall that you're stuck with. After awhile, you'd like other spaces to choose from even if they are similar. Unable to find other IR's, you might turn to an algorithmic approach.

JCJR
KVRAF
2352 posts since 17 Apr, 2005 from S.E. TN

Re: Moog String Filter

Post Mon Mar 28, 2016 7:46 pm

Thanks that signalwizard device sounds impressive on the demo recordings. It is surprisingly inexpensive. So often people will make a unique product then price it so high that only insane people will buy it. Some years ago at NAMM I think it was yamaha, maybe some other big company, had a huge booth rolling out rather fancy beautiful looking new electric violins, cellos and basses. I asked one of the fellas at the booth if they planned to release some kind of body resonator stompbox for the instruments. He looked at me like I was a crazy man. Well, he may have been right, but it seemed a reasonable question anyway. :)

Your tetra demo sounds good as well.

Maybe you have added some reverb to your tetra track, in addition to the impulse response? Or not? The signalwizard demo unprocessed electric violin is honestly recorded dry as a bone. The processed tracks sound fairly dry, but sound like a little bit of ambience, very short reverb or something was added along with the resonances.

I doubt if they added reverb for sweetening but dunno. Am guessing maybe they just use fairly long impulse responses, and the impulse response adds the perceived ambience (along with the resonances)? It would seem to make sense, because if one thunks a violin body it will ring a fairly long time. So far as I recall. Has been some years since I thunked a violin body. May be remembering wrong.

If it is a long impulse response adding the "live" ambience, then that may be something clearly superior to an IIR filter bank? I don't recall that my Moog Freeman resonator bank had high-enough Q to ring long enough to sound like it was adding even the slightest hint of reverb ambience. Raising the Q of an IIR filter bank high enough to get long enough ringing to sound like a touch of short reverb-- Maybe at such high Q's the filter bank would sound more like a huge chorus of cheezy 1960's drum machine bongos, rather than violin ambience? :)

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Chris-S
KVRAF
2605 posts since 10 Nov, 2013 from Germany

Re: Moog String Filter

Post Mon Mar 28, 2016 11:59 pm

JCJR wrote:Thanks that signalwizard device sounds impressive on the demo recordings.
Yesterday I had some fun to play a simple saw wave through the stradi impulse which I created from the demo samples.

Beside of the resonances a very big factor for realism is to play with articulation.

- Amount and rate of vibrato
- Random tremolo
- Light random detuning in the attack phase

PS: http://www.soundonsound.com/sos/May03/a ... rets49.asp

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Chris-S
KVRAF
2605 posts since 10 Nov, 2013 from Germany

Re: Moog String Filter

Post Wed Mar 30, 2016 5:21 am

@Leslie:

"Tetra" is the Dave Smith hardware synth?

Chris

http://chris-s.bplaced.net/div/Geigente ... 160320.mp3

Leslie Sanford
KVRAF
1597 posts since 4 Dec, 2006

Re: Moog String Filter

Post Wed Mar 30, 2016 6:58 am

Chris-S wrote:"Tetra" is the Dave Smith hardware synth?
Yeah, it's basically a Prophet 08 in a box with half the polyphony. It's a nice synth with some pretty flexible modulation routings.
Nice! I like the pull-offs and hammer-ons. The sound very natural. And the overall tone is good, too.

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Chris-S
KVRAF
2605 posts since 10 Nov, 2013 from Germany

Re: Moog String Filter

Post Wed Mar 30, 2016 7:18 am

It is u-he Beatzille (nice sounding saw ;) ), ReaVerb loaded with stradivari impulse, ReaEQ and Sanford Reverb. :tu:

Leslie Sanford
KVRAF
1597 posts since 4 Dec, 2006

Re: Moog String Filter

Post Wed Mar 30, 2016 4:47 pm

Chris-S wrote:ReaVerb loaded with stradivari impulse
I didn't realize that Reaper had a convolution reverb built-in!
ReaEQ and Sanford Reverb. :tu:
:D

Here's an attempt at imitating a staccato cello articulation:

http://www.lesliesanford.com/music/temp ... est-01.mp3

Envelope times and modulation depths tied into key velocity is critical to getting it right. Also, key scaling is important. It's got a ways to go, especially in the higher register.

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Chris-S
KVRAF
2605 posts since 10 Nov, 2013 from Germany

Re: Moog String Filter

Post Wed Mar 30, 2016 11:34 pm

Leslie Sanford wrote: I didn't realize that Reaper had a convolution reverb built-in!
It comes with a zero latency (ZL) option, Reverb builder and an impulse generation tool. :tu:

Unfortunately it's not included in the free ReaPlugs package (for other DAWs).

camsr
KVRAF
6879 posts since 17 Feb, 2005

Re: Moog String Filter

Post Wed Mar 30, 2016 11:36 pm

What's going on with these convolutions? I just got lost there!
Image

Leslie Sanford
KVRAF
1597 posts since 4 Dec, 2006

Re: Moog String Filter

Post Thu Mar 31, 2016 11:10 am

camsr wrote:What's going on with these convolutions? I just got lost there!
You know how you can use an impulse response of a concert hall with a convolution reverb to make it sound as though you're in that same concert hall? It's the same principle. You can use an impulse response of an instrument with a convolution reverb to make it sound as though your synth is being played through the same space. It's a way of giving body to a sound.

sprnva
KVRian
1331 posts since 16 Jan, 2013

Re: Moog String Filter

Post Thu Mar 31, 2016 11:34 am

camsr wrote:What's going on with these convolutions? I just got lost there!
I agree! It's quite convoluted!

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