[Csnd] code share: Max Mathews phasor filters (I think)

I've been meaning to look into this for some time. I think these are
the phasor filters that Max Mathews was working with as a sort of live
collaborative tool. In any case, the actual filter is described here:

They are resonators with very narrow bandwidth so I could imagine this
being used for creating resonant filter banks. You can tune the
frequency arbitrarily with no issues so you can do FM on the filter
and this can be an interesting effect.

I've made a UDO with some examples where I've tried to see what kind
of things it can do. You can find it here:

!!!WARNING!!! - if you want to try using the UDO outside of these
examples, it can and will blow up and produce very loud output if you
put a continuous signal through them that doesn't have a VERY small

Warnings aside, hopefully it's of interest to someone :slight_smile:


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Thanks for that! Some interesting sounds... Some exploration is indicated,
I think!

  -- Pete --

Very interesting, Joel. Thanks for sharing

Prof. Victor Lazzarini
Maynooth University

Thanks. This is great.

Thanks for making and sharing Joel,

This is such a nice UDO and some nice demos too - rich with possibilities!

You might be interested to know that Max Mathews wanted me/us to add his phaser filters to Csound as opcode and gave me all of his source code, back in the day.
At that time, some years ago now, I shared the code with John ffitch and I thought that we might have added a version of it as the phaser1 and phaser2 opcodes.

  • I was mistaken and confused by the fact that the McCurdy Collection (awesome all of them!) has examples of these as “specialized filters” and uses them with widgets as filter banks and resonators.

Max and I would play concerts all the time together in which he would jam on his “Phaser Filter system” from a MIDI controller box that I had given to him.

  • He will loving doing live remixing with them in his studio and for my students in classes he would give at Berklee, and he even shared with me that
    he was happily experiencing this new “career” as a performing DJ! :wink:

The phaser1 and phaser2 opcodes in Csound have great manual examples too - and in them, and on these super manPages one can cleary see, read and render(hear) that these are related to the classic phaser and flanger effects boxes and algorithms.

And so, for sure it would be great to have these filters added to Csound as opcodes!

And, in the same way, that we ‘honor’ Sean Costello for his fantastic waveguide reverb algorithm - the reverbsc, I would propose that these become the:
mvmfilters - max vernon mathews - mvm was his login
some such honorific

which also makes me think about his and my dear friend Jean-Claude Risset and wonder if we might also have a need for a rissetoscillator (endless) or a rissetrhythm (metro) type opcode too?

  • to compliment the Euclidean rhythm opcode that I am hoping that Steven Yi and Rory Walsh will be collaborating on and adding to the next release :wink:

Thanks again Joel for bringing back such wonderful memories and bringing forward more wonderful possibilities.


I would like to give this a go. I'll see if I can make an opcode out
of it. Hopefully John ffitch or Steven Yi can point me in the right
direction if I run into trouble.



I will be happy to share the source code from Max Mathews with you.

  • maybe it will help
  • but, I think you already have a great sounding UDO

What Max like to do was have about 16 filters in his resonator bank (maybe this would be one of the modes or variations of the module)

Victor is pretty good with filters too :wink: and might offer some help?

Hi Joel,

This is great, thanks for sharing! Happy to help with any native
plugin translation issues.

All best!