I'm often asked "Why bother with single-string effects processing when there are so many great guitar pedals and effects processors out there?"
The answer is: "Because it opens up a whole new world of sounds!"
Let's start by reviewing typical monophonic guitar effects' limitations (I am not including the BOSS/Roland guitar synthesizers in this category):
Mono inputs contain all string signals. There are some stereo input pedals, but these are typically preceded by an effect with separate dry and wet outputs, which are also "mono" signals in their own right.
While there are some pedals with string pitch detection, these require serious Digital Signal Processing (DSP) and typically do not output individual string audio.
The pedals apply effects to all strings simultaneously, which immediately compromises the ideal settings for each string. For example:
Intermodulation distortion is introduced which makes the sound "muddy"
Auto Wah frequencies and ranges are not optimized for each string
Phasers and flangers have the same issues as auto-wah
Compression and sustain settings need to be quite different for low frequency strings vs high frequency strings
Guitarists typically do not recognize these issues unless they have experienced single-string processing. It's like having listened to MP3s on cheap earbuds all your life and suddenly being exposed to Dolby Atmos theater sound - the revelation is eye-opening! After that, the earbuds never sound the same.
OK, so how does one try out single-string processing?
Provide single-string audio
Install a divided pickup on your guitar (or buy one ready-made!). There are many such guitars out in the marketplace, primarily geared towards creating synth-like sounds, such as the GK system by BOSS/Roland and Fishman Triple Play (FTP).
I'm afraid none of the above are ideal for single-string processing. The reason is that the GK and FTP pickups have been designed to provide a signal for pitch detection and have a very poor natural audio sound. No equalization in the world can make them sound as good as your traditional guitar pickups (believe me, I tried!).
You could start with a GK guitar to try out single-string processing, with the understanding that your pickup is the limiting factor for good tone and will likely need to be upgraded at some point.
Individual string piezo pickups on the other hand sound much better. My preference is for the outstanding RMC pickups, with LR Baggs and Graph Tech as second and third. Their wider frequency response allows for a good amount of equalization and nice tone. They will always sound clean and "acoustic" though, so perhaps that may not be the tone you are after. I think that is not as much of a problem, since they respond well to distortion and filtering.
By far the best divided pickup for single-string processing currently available is the Cycfi Research Nu Multi series, which can be configured to any number of strings! These are low noise, humbucking, low impedance magnetic pickups in miniature packages. The frequency response is very wide and flat, lending itself to great equalization schemes and pickup simulation algorithms.
Note that string cross-talk is not as important as with the pitch-detection applications. Palm muting works splendidly as well.
Set up one effects channel per string
This is where the rubber meets the road. Your options are:
Clone your pedalboard. Just kidding: this is ridiculously expensive and complex. That hasn't stopped folks from trying! However, you should tally up how much your pedalboard cost you and multiply this by the number of strings you want to process. The total will give you a cost comparison for your final solution. It puts everything in perspective!
Use a Digital Audio Workstation (DAW). This is a good solution for those who want to construct songs track by track and are not playing live. You will need a studio-quality audio interface with enough channels and a fairly powerful computer to handle effects processing in real time during recording (you could also apply them later, but that makes it much harder). The main problem is controlling your effects; you will have to use a mouse (I don't know about you, but I can't operate a mouse while playing guitar) and MIDI controls or convert control voltages (CVs) to MIDI, which gets very complex very quickly. Then you need to invest in all the effects plugins you want. Add up all those costs and compare them to your cloned pedalboards. You might be surprised!
Use multiple effects processors. I have a friend who uses three AxeFX processors in parallel for his six string guitar. Now there's a big budget! The downside is that you're limited to what the box provides, no modifications possible. This works fine as long as you don't want to control all three in unison.
Use Eurorack modules. This approach is the most flexible and essentially allows for an infinite combination of audio paths, effects, and modulations. There are two main options here:
A virtual modular system. VCV Rack and Voltage Modular both run on a computer and allow you to construct a virtual modular effects system. All you need is the audio interface mentioned above to import the single-string guitar audio. As with the DAW solution, control is either via a mouse or MIDI. This is a great way to find out if modular is the way to go for your needs; a lot of modules are free so the investment is minimal.
A hardware modular system. The choices here are amazing - about 9,700 modules are available commercially at the moment and the selection is growing exponentially. Think of it as a set of individual string pedalboards in different form factor. SynQuaNon has developed a series of hexaphonic modules that save space and money over buying six modules for each effect type.
The Eurorack modular ecosystem is future-proof in that one can add and take away modules to create new sounds forever. You can start very small and build it up as you go, thereby avoiding a large initial investment (what was your cloned pedalboard total again?).
One huge advantage of Eurorack modular is the ability to introduce Master effects parameter controls, as well as easy on-guitar CV pot and expression pedal interfacing. No MIDI necessary, but OK if you want it.
The other unique feature is that everything is CV controlled - CVs can be DC, low frequency, or audio. They can be mixed, chopped up and modified in a million ways to create incredible modulation for effects parameters. Sequencers are amazing CV generators. Seriously cool!
But I need my presets, what about that? There are a number of ways to store audio and CV settings as presets in Eurorack; one simply has to search for the right modules. Not only can static settings be stored and recalled, one can record CV automation just like in a DAW!
For single-string processing one does need to pay attention to unwanted noise, so check out my blog post on creating the cleanest sounding modular system.
Experiment with single-string effects
Now let's have some fun! Here are some (but by no means all) suggestions for things to try:
Effects on Groups of Strings (Splitting the Fretboard)
Multi-channel Pitch Shift/Harmonizer
Multi-channel Ring Modulation
There are many other possibilities. Check out the demo videos in this blog for ideas!
Decide on how to route the channel outputs
Don't just mix down to mono or stereo! Another interesting possibility is creating multi-channel outputs; at first I experimented with the single-string channels fed to individual amplifiers and speakers, but this is not always musically pleasing. Check out different forms of Psycho-acoustic Sound Distribution instead. Dolby Atmos Surround Sound is an exciting possibility with growing market support.
For more information, please feel free to contact SynQuaNon via the website or our Facebook page. Now go make some music!