Guitar FXBOX – Part 1, the software

I haven’t blogged about the guitar before, although this is the conventional instrument I play.

There are enough places on the web to find descriptions of commercially produced effects – of which there are many thousands – and, with possibly one or two exceptions, I won’t be writing about these.

However, I thought it might be worth describing some which I’ve been using which were written using PureData and which together I’ve called the ‘FXBOX’.

Some of the effects I’ve bought have cost £100 – £200, but for no extra expense other than a computer – which I assume you must have, as you’re reading this – and a little know-how, all these effects and more are available.

I have to say, I didn’t write the majority of these effects myself. The know-how has come from examples in tutorials or instructions for PureData, like this one: http://en.flossmanuals.net/PureData/ or this one: http://pd-tutorial.com/ or from the PureData forum at http://puredata.hurleur.com/.

A particular inspiration was Pierre Massat’s ‘Guitar Extended’ blog. Pierre has developed a sophisticated system using an Arduino and a Raspberry Pi to make and control the sound of the guitar, which you can read about in detail here: http://guitarextended.wordpress.com/.

In my case, there were a small number of particular effects I wanted to combine in a single unit, and my good fortune was to find this Spectral Delay patch by Pierre Massat (from an original by Frank Barnecht, based, in turn on work by Johannes Kreidler, whose tutorial is referenced above): http://guitarextended.wordpress.com/2012/02/07/spectral-delay-effect-for-guitar-with-pure-data/

This became the central element of the FXBOX project. What is does is to give different delay times to different harmonics of the input, producing an effect which Pierre likens to ‘hundreds of sparks or stars that fall like raindrops or broken crystal’ – a poetic, but apt description. More conventional echo effects are also available from this patch.

In the FXBOX I put a couple of conventional effects before the Spectral Delay, namely Chorus and Distortion, and a variable attack patch; at the end of the chain I added patches for panning and stereo imaging. The two interesting effects which remain are a pitch controller – the normal guitar input can be raised or lowered by up to an octave – and an unusual ‘freeze’ effect, which can produce either a static drone or a very odd series of pitches in response to the input.

This screenshot of the main page shows the various effects and their controls: I’m very grateful to Pierre and others for making their patches available for everyone to use.

One or two people whose patches came from posts on the Pd forum, I know only from their online names: ‘ralf’ for the Freeze function [http://puredata.hurleur.com/sujet-6100-fft-freeze-help], and ‘dack’ for the Pitch Shifter from his ‘Guitar multi-effects rig’ [http://puredata.hurleur.com/sujet-2525-guitar-multi-effects-rig].

The various patches which are required to make the FXBOX work are here [Edit:  these are the revised files after changes described in Part 3 of this post]:

http://www.andymurkin.net/Electronica/FXBOX/abswitch~.pd

http://www.andymurkin.net/Electronica/FXBOX/crossfader~.pd

http://www.andymurkin.net/Electronica/FXBOX/expression.pd

http://www.andymurkin.net/Electronica/FXBOX/FXBOX22.pd

http://www.andymurkin.net/Electronica/FXBOX/Guitar_specdelay~.pd

http://www.andymurkin.net/Electronica/FXBOX/LoopGenerator.pd

http://www.andymurkin.net/Electronica/FXBOX/midiin.pd

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All the variable controls are available on the screen, but I decided for practical performance purposes it would be best to have presets which could be selected quickly.

In addition, after starting to use the FXBOX, I rapidly came to the conclusion that it needed a controller which was easier to use than the laptop trackpad. For one thing, you can’t adjust a setting manually and still keep playing. So I set about designing a controller which would also be compatible with PureData. Some controls might practically be operated by hand, but essentially this would have to be a foot controller with buttons and pedals for the various presets, and for adjusting settings which might need to be changed while playing.

The second part of this post describes the controller.