GNU RADIO

Fancy following in the footsteps of Hendrix or Clapton? Mike Bedford shows you how to add 70s-style electronic effects to your music tracks.

OUR EXPERT Mike Bedford admits to being a fan of analogue music – vinyl discs and all. Despite that, he’s really enjoyed digitally altering some of the classic rock music of the 70s.

For centuries, making music had relied on the simple principle of objects vibrating when they’re plucked or hit, or columns of air vibrating as that air is blown through a pipe. This changed with the popularity of early electric organs – most notably the Hammond Organ – in the 30s, 40s and 50s, but widespread change didn’t come about until the 60s and 70s. This was the dawn of rock music, and marked a real growth in electronic music. One important element of 70s electronic music was the synthesiser and we looked at this technology in LXF268, when we saw how to recreate the Doctor Who theme tune.

Synthesisers generated musical notes purely synthetically, but a different approach was also a part of the sound of the 70s. This alternative form of electronic music involved generating the notes using the timehonoured tradition of plucking or hitting something – most typically the strings of an electric guitar – and using electronic circuitry to modify the sound.

Two of the best-known effects – which surely epitomise 70s rock – are fuzz and wah-wah. These effects were originally implemented using analogue electronics, but they can be replicated digitally, and that’s our theme here. Using a hands-on approach, we’ll show you some of the physical principles of electronic musical manipulation, and go on to see how you can recreate the effects, starting with ordinary guitar music and transforming it to something that Jimmy Hendrix would have been proud of.

Under the hood

The software tool we’re using is called GNU Radio Companion and it’s available in all the main repositories. It was designed specifically for designing softwaredefined radios (SDRs), but it’s equally suitable for trying out audio effects. And unlike turnkey software that’s designed for real-world use, you can easily see what’s happening because of its excellent range of visualisation tools.

First of all, we’re going to investigate fuzz. You’ll almost certainly have heard it, even though you might not have been able to name the effect, so let’s start by describing it as a form of distortion. Normally in audio, that word has negative connotations. However, although you certainly wouldn’t want to apply it to all the instruments and vocals in a track, it can add something rather special if you apply it to a guitar. So, before firing up GNU Radio Companion, find a suitable electric guitar track – one that doesn’t already have any effects applied – converting it to a WAV file if necessary, perhaps using an online utility or Audacity, because GNU Radio Companion doesn’t support MP3 files. For now, we suggest using any electric guitar music, although when we move on to more practical solutions, we’ll make some more concrete recommendations of suitable tracks.