| Hello,
I'd like to have a bandpass where I can increase the
Q until it starts self-oscillation, just like
the moogvcf, but with bandpass characteristics instead
of the lowpass. (And, just for the completeness, the
same with a highpass characteristics).
Is there an easy way to modify the moogvcf sources
so to have a bandpass instead of a highpass ?
What I will try tonight is split the input in 2
branches, then filter one with moogvcf, and the
other with a butterhp at the same cutoff, then
sum the two filtered signals at the end. I'm,
however, not sure if it will do what I expect...
Any ideas ?
Thomas
PS: I need it for trying to make Goa-Trance.
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Date: Tue, 13 Apr 1999 11:29:43 -0400
From: Mike Berry
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To: Thomas Huber , csound@maths.ex.ac.uk
Subject: Re: Ringing bandpass ?
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Basically, the ringing in moogvcf increases as it more an more approximates a
bandpass filter anyway. As the resonance is increased, you get a more and
more prominent bump at around the cutoff frequency. At some point, the pass
band of the bump looks a lot like a bandpass, except that the low side is
somewhat higher than the high side (though both are small compared to the
"passband"). So you should be able to get a similar effect with a narrow
bandpass with a lot of amplification, so that almost no matter what you put it
you get the center freq out (i.e. self-oscillation). The major practical
difference is going to be getting a similar gain response. You are probably
going to have to drive the bandpass harder to get the response you are looking for.
--
------
Mike Berry
mikeb@nmol.com
http://www.nmol.com/users/mikeb
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Date: 13 Apr 99 15:37:05 America/Fort_Wayne
From: Robert Junior Mcnulty
To: csound@maths.ex.ac.uk
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Subject: wgpluck
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How does wgpluck work? I lost my computer version of the manual.
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Date: Tue, 13 Apr 1999 10:24:06 -0700
From: Sean Costello
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To: Thomas Huber
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Subject: Re: Ringing bandpass ?
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Thomas Huber wrote:
>
> Hello,
>
> I'd like to have a bandpass where I can increase the
> Q until it starts self-oscillation, just like
> the moogvcf, but with bandpass characteristics instead
> of the lowpass. (And, just for the completeness, the
> same with a highpass characteristics).
How about using a RESON filter, with the bandwidth selected as a very
small fraction of the cutoff frequency (for very high Q), and normalized
to 1? It won't self-oscillate, but it will ring for a good long time
when excited by a signal.
As far as converting the moogvcf to a true bandpass filter, I don't
think it can be done. In the analog realm, cascade-style filters were
never used for bandpass - a state-variable filter was the filter
normally used (Csound might have a Chamberlin style state-variable
filter; if not, I might try and code one soon). A Moog highpass would
be possible, but it probably wouldn't self oscillate; highpass filters
of the Moog topology generally don't. The only oscillating highpass
filter I know of was the Sallen-Key highpass used in the Korg MS-20, and
I don't know of any digital equivalent of a Sallen-Key filter.
Does the moogvcf opcode self-oscillate? I am under the impression that
no digital filter self-oscillates without an initial source of
excitation, but I could be wrong.
As far as making Goa-Trance, don't get hung up on the fact that none of
the Csound filters sound as good as a 101 filter (well, the moogvcf
sounds pretty Rolandy). If one filter doesn't cut it, try 2, or 5, or
20. Lots of great sounds can be made with several reson filters in
parallel.
Sean Costello
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From: David Boothe
To: 'Robert Junior Mcnulty'
Cc: 'Csound'
Subject: RE: wgpluck
Date: Tue, 13 Apr 1999 13:18:30 -0500
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The documentation for wgpluck was returned to the version 3.53 pdf manual,
after being absent for a while. Below is the page (in text format).
-David.
8.20 wgpluck
ar wgpluck icps, iamp, kpick, iplk, idamp, ifilt, axcite
8.20.1 DESCRIPTION\
A high fidelity simulation of a plucked string, using interpolating
delay-lines.
8.20.2 INITIALIZATION
icps - frequency of plucked string
iamp - amplitude of string pluck
iplk - point along the string, where it is plucked, in the range of 0 to 1.
0 = no pluck
idamp - damping of the note. This controls the overall decay of the string.
The greater the value of idamp1, the faster the decay. Negative values will
cause an increase in output over time.
ifilt - control the attenuation of the filter at the bridge. Higher values
cause the higher harmonics to decay faster.
8.20.3 PERFORMANCE
kpick - proportion of the way along the point to sample the output
axcite - signal which excites the string
A string of frequency icps is plucked with amplitude iamp at point iplk. The
decay of the virtual string is controlled by idamp and ifilt which simulate
the bridge. The oscillation is sampled at the point kpick, and excited by
the signal axcite.
8.20.4 EXAMPLES
The following example produces a moderately long note with rapidly decaying
upper partials:
instr 1
axcite oscil 1, 1, 1
apluck wgpluck 220, 120, .5, 0, 10, 1000, axcite
out apluck
endin
whereas the following produces a shorter, bighter note:
instr 1
axcite oscil 1, 1, 1
apluck wgpluck 220, 120, .5, 0, 30, 10, axcite
out apluck
endin
> -----Original Message-----
> From: Robert Junior Mcnulty [mailto:robertjunior@usa.net]
> Sent: Tuesday, April 13, 1999 10:37 AM
> To: csound@maths.ex.ac.uk
> Subject: wgpluck
>
>
> How does wgpluck work? I lost my computer version of the manual.
>
>
> ____________________________________________________________________
> Get free e-mail and a permanent address at
> http://www.netaddress.com/?N=1
>
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Date: 13 Apr 99 20:38:00 America/Fort_Wayne
From: Robert Junior Mcnulty
To: DBoothe@lyrick.com
Subject: book
CC: csound@maths.ex.ac.uk
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I just found the manual again. Adobe has a new reader. It should be able =
to
read this one.
I don't have the address, but you can do a search by typing "Adobe Acroba=
t
Reader" in Excite!
See you later.
And thanks for the page from the book, David.
I am going to work on the DX7 emulator. I think I understand it.
Robert
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From: Richard Dobson
Organization: Composers Desktop Project
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I have just downloaded and installed the new Winsound and sources;
Yes, indeed, there are some required files not listed in winsound.mdp -
from the 100 or so link errors I have, possibly several; so far I can
see that biquad.c and aifc.c need to be added.
[this show how long since I last built Csound; I've been several
versions behind for a while - shame on me!]
Also, funnily enough, a file is missing from the zipfile that
winsound.mdp does contain - aoscilx.c.
I have also found that the realtime playback doesn't work under NT4 0 -
it hangs completely at the start. Seems to work OK under Win95. I see
there have been some changes from the last version I worked on. Perhaps
it is time I offered my NT-friendly playback code for incorporation.
Also, I agree with John that some threading would be good - the Winsound
window is utterly immoveable and unresponsive during playback, and it is
of course quite un-stoppable other than with Ctrl-Alt-Del.
I'm off to sunny Wales until Saturday - so will be unable to to do any
programming...just added Linux to my machine too... ~:-[
Richard Dobson
Xopher wrote:
>
> Yes, I understand, but several files have been added and a few removed since
> then. Thus, one must go through and selectively add files as necessary.
> Basically, there will always be new files, because every opcode has a source
> file. In addition, the source code contains mk, mk1, lk1, and tgt files
> dated 3/19/99. I assume these files to be makefiles for other compilers.
> But it is my understanding that a MS compiler is used for both Winsound and
> Consound, and the appropriate makefiles date from May and June last year.
> So my question remains... Why aren't the Windows makefiles updated?
>
--
Test your DAW with my Soundcard Attrition Page!
http://wkweb5.cableinet.co.uk/rwd
CDP homepage: http://www.bath.ac.uk/~masjpf/CDP/CDP.htm
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Date: Wed, 14 Apr 1999 11:14:44 +0200 (MET DST)
From: Thomas Huber
Subject: Newest PPC Version of csound ?
To: csound@maths.ex.ac.uk
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Hello,
A friend of mine has a power Mac, and he would like to begin with
csound, also (I 'triggered' his interest (-; ). Now he has found
version 0.2.0b ... Of course it does not understand all the cool
new opcodes. On the dream ftp site, I found version 3.49, which is
already better.
But is there also a version 3.53 for PPC ?
Thomas
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From: Thomas Huber
Subject: Re: Ringing bandpass ?
To: csound@maths.ex.ac.uk
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> How about using a RESON filter, with the bandwidth selected as a very
> small fraction of the cutoff frequency (for very high Q), and normalized
> to 1? It won't self-oscillate, but it will ring for a good long time
> when excited by a signal.
I will try. For the moment, I'm using moogvcf with high Q settings
as suggested by Mike Berry. It works quite well.
>
> As far as converting the moogvcf to a true bandpass filter, I don't
> think it can be done. In the analog realm, cascade-style filters were
> never used for bandpass - a state-variable filter was the filter
> normally used (Csound might have a Chamberlin style state-variable
> filter; if not, I might try and code one soon). A Moog highpass would
A state-variable-filter - oh yes yes, please, could you code one ?
I'd love to have another excellent sounding filter like 'moogvcf'.
And as far as I know, the state variable filter can be used as
lowpass, bandpass, highpass and notch (band-reject) at the same time,
depending on where you take the output (in the analog circuit, I have
no indea how it is in the digital implementation). So we would have
another cool filterset, let's say 'statelp', 'statebp', 'statehp',
'statebr'. I'm looking forward for it. In the meantime, I work with
what's already there, and that's quite a lot. Wait for my second song.
Already now it is _much_ better than the first (which I called second (-;),
and it's not even finished. This will become a real song you could play
at a party, not just a first test like the other one I put on my ftp
site recently...
> Does the moogvcf opcode self-oscillate? I am under the impression that
> no digital filter self-oscillates without an initial source of
> excitation, but I could be wrong.
It does self-oscillate, yes. I think that the moogvcf is not a classical
digital filter, it's a simulation of an analog circuit filter
Thomas |