Thursday, 4 June 2020

Guitar Effects Pedals that don't seem to exist...

There are a lot of guitar pedals out there. The more you look, the more you will find. A fascinating recent (well, recent-ish: they've been doing it for ages, but now it seems to have been noticed!) trend is keyboard players using guitar pedals to process their keyboards, and so you now have stereo in and out, very high quality, smoothly sophisticated 'effects' boxes like the Strymon 'Big Sky' (and others). There are some fascinating YouTube Channels on the topic too - JHS Pedals is a stand-out example, and Josh Scott is a totally watchable, hugely informed, completely immersed 'pedal' guy, and imho he is one of the best of many...

So you would be forgiven for assuming that you can get commercial pedals that do just about anything. I certainly thought that this was the case, based on everything that I've ever seen, plus spending 3 days at NAMM in Anaheim once - something that I think every hi-tech musician should do once in their lifetime! So no-one was more surprised than me when I couldn't find a pedal that did something that is one of the standard features of my track strips in Ableton Live:


Actually, nowadays I usually have an Effects Rack that has common controls for the Auto-Filters plus two separate Auto-Pans set to act as two individual mono Tremolos. Sometimes I hark back to the S&H Filter sound by doing this to the tremolo...


Anyway, I've been planning an update to my live rig for a while now, and so one obvious thing to add to the spreadsheet was a Filter/Tremolo pedal... So I looked for one.

And I looked for one.

And I tried harder, assuming that I was calling it the wrong thing. I obviously wasn't looking properly...or in the right places, or in obscure places... or in very obscure places...

 But I didn't find one. Which kind of broke my assumption that there were:

Pedals that can do anything you might want!

But, of course, there are! You just need to go outside of commercial 'off the shelf' pedals and into 'program your own' pedals. So I reached for my 'go to' solution : the Rebel Technology OWL Pedal. Originally purchased because a 'name' producer asked me if I could make a pedal that did something really unusual, which I did, and it has been with me ever since! It gets used some of the time as a rapid prototyper for ideas, as well as part of my live rig when I don't want to take a full pedal board with me.


Programming simple audio processing concepts like 'filter followed by tremolo' is completely within the remit of Cycling 74's Gen, which is the lower-level, sample-rate processing, high performance bit of Max (and MaxForLive). It took me a few minutes to have a prototype up and running, and slightly longer to get that onto the OWL pedal because I'd forgotten how to do it since I last did it. I'm intrigued by the way that modern life has all sorts of complex processes that you can learn, use intensely for a few days or weeks, and then not use again for months, and by then you've forgotten the fine details. Maybe I'm just the Patrick Stewart version of Professor Charles Xavier, and not the James McAvoy version...

Inside...

Anyway, here's the startlingly non-innovative code in Gen:


Yes, that's a resonant low-pass filter, two LFOs and two multipliers acting as VCAs. Having two LFOs modulating the volume of two channels is something that I like because you don't hear it very often - it is easy to do auto-pan across the stereo image, but this isn't that, it is two-channel mono tremolo with the outputs panned hard left and right. On drums, it gives a little bit of animation, but it definitely isn't the 'panning back and forth across the stereo image' that you sometimes hear. Probably not a 'gated reverb' that will become THE sound for a while, but I think it sounds interesting, and it was different until I wrote this...

Should you want it, you can now find my 'DrumTrem' patch on the Rebel Technology web-site, which kind of proves that there really are:

Pedals that can do anything you might want!

It's just that they may not be available 'off the shelf', and you may need to program them yourself. 

Beyond

Apart from the OWL Pedal, there are pedals like the Mod Duo, the Mod DuoX, the Empress ZOIA, the Zynthian, as well as more computer-oriented devices like the Blackaddr Arduino Teensy Guitar Audio Shield (lots of options!), Axoloti, Aida DSP, and the Bela.io / Rebel Technology SALT module, as well as the modular version of the OWL pedal from Rebel Technology. There are lots of other examples out there, because this is a fertile area for Kickstarter and Indiegogo projects, and lots of undergraduate computer science students keep having the same idea of making a programmable effects pedal... Programming languages for all of this diverse range of hardware solutions are just as varied: C, C++, Gen, PureData, Faust, LV2, Nyquist, BALibrary or PJRC's Audio Library for the Arduino Teensy Guitar Audio Shield, and various varieties of assembler for SHARCs, Cortexes, Spin FV-1, and more. In this paragraph I have gone through a huge range of possibilities: from simple 'visual programing' stuff to VSTs to low-level DSP assembler, and commercial through kits to DIY homebrew. This list is in no way comprehensive - it is an incomplete sampling of the available. Do not be overwhelmed. The rabbit hole basically goes as deep as most people can cope with, and then well beyond that...

(Be cautious when pledging to audio and music products and kits that are crowd-funded - make sure you understand what you are doing when you make a pledge... Also you should be aware that some audio and music products and kits may be from very small companies, and so the availability, support and longevity may vary... As always: do your research before parting with your money!) 

My days of writing DSP code on Motorola 56Ks are long-gone (along with the pizza and cola diet), so I'm perfectly happy with high level abstractions like Max, and slightly lower level sample-rate 'critical section' stuff like Gen. But I'm sure that some readers are already planning on reading up on Analog Devices' SHARC assembler... 

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Modular Equivalents

In terms of basic modular equivalents, then implementing DrumTrem is pretty straight forward: you just need 2 VCFs, 2 LFOs, and 2 VCAs, although you could add 2 extra LFOs to drive the VCFs cyclically as well. Anyway that is an ME of either 6 or 8. One of the often overlooked advantages of modular synthesizers is that you can easily do exactly this type of unusual effects routing and tweaking. My advice would always be to explore the flexibility that modular patching gives you, and not to just make a modular equivalent of an ordinary monosynth because that's what you are familiar with...

Pedal Equivalents

This is trickier. Whilst you can find various EQ pedals, a straightforward low-pass resonant filter is much rarer, and finding one with easy access to controls like Cut-off Frequency can be awkward. I found several pedals which were variants of auto-wah, and which had minimised the number of rotary controls, and so didn't really give you access to the simple cut-off frequency control (and resonance) that I like. Tremolo pedals seem to be mono, and so you would need two of them to get the dual rate two-channel tremolo that I mention here. All in all, this might be an expensive way to see what it sounds like!

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