Custom Wah Effect
After hearing some subtle yet effective use of the wah-wah pedal on Yusef Lateef’s album, Yusef Lateef’s Detroit Latitude 42º 30º Longitude 83º, I was compelled to attempt writing my own “wah” effect patch in Max/MSP.
I’ve been tinkering with this patch for a few days now, and even though I know it’s surely not perfect, I think it sounds reasonably cool. Also, I’m tired of messing with it, so I figured I just post it here for anyone interested, or anyone who can provide some advice on how to make it better. Here is a short sample.
Bear in mind this sample is to display the sound of the effect not my guitar playing. I didn’t spend much time focussing on “getting guitar part right” if you know what I mean.
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If you like, please feel free to download a copy of this .maxpat here.
I think it’s a decent first effort, but there are some digital “noises” that I hear in the patch that make it slightly unappealing to me.
The Research
First, I did a small amount of research on the frequency range I should be working with. I used this page as a quick reference for the ranges, and this page as a more in depth explanation, complete with schematics. I don’t understand electrical schematics so thoroughly, but the page served as good a springboard for ideas.
This is what the final patch looks like:
Besides the guitar playing on Yusef Lateef’s album, I was also inspired by a tutorial on the Cycling 74 website on creating a Max5 guitar processor. Specifically, I was interested in the Adding an EQ/Filter section during part 2.This section of the tutorial is great because it very simply explains how to effectively combine a variety of filters to be used on a signal.
The Process
I estimated a workable range for the [filtergraph~] objects from the first two websites that I mentioned above. After some experimentation, I settled on 400Hz to 1800Hz, with decibel range of .0625 to 16..
I also decided that using two filters moving in opposite directions would be the way to go for maximum “wah” effect. As the bandpass filter on the left moves up through the frequency range, the resonant filter on the right will move downwards.
The expression pedal that I use with my keyboard is a Roland EV-5.
The patch is set up to receive the midi data from the pedal and scale it to the desired frequency range. Because I want the resonant filter to move in the opposite direction from the bandpass filter, I used a combination of [* -1] followed by a [zmap] object to reverse the data values.
Finally, the two filters get combined via the [pak] object like in the tutorial I mentioned above, and now we can use this effect on whatever comes in through the [ezadc~].
Conclusion
Like I said it’s not perfect, but it sounds alright to have some fun with, and more importantly, I was able to enjoy playing with dynamic filter effects and live audio. Maybe I can create some more interesting effects if I remove the limitation of trying to replicate a piece of gear that is probably best made from resistors and capacitors.
It would also be nice if I could make a VST/AU version of this to use within a DAW, however, Max/Msp is not going to allow its users that functionality unless they purchase Max for Live, and even then, your plugins will only work with Ableton Live.
Don’t get me wrong here. Ableton is awesome! Hopefully one day I have enough money to buy Live 8, but considering the price of Max5, Ableton, and now Max for Live, it looks like a sound designer/musician would have to drop roughly $1500 just to create effects with Max in Ableton. Seems a bit extreme.
