Edit Acoustic Guitar Recordings to Perfection

Edit out acoustic guitar artifacts for a "perfect" recording

by Craig Anderton

Of course, this assumes you want perfection—sometimes it’s the little noises, squeaks, and glitches that add a “human” quality to a performance. However, it's possible that those glitches may step over the line, and become problems that distract from a part. For example, with drums, there’s little point in quantizing drums to a grid if they don’t sound wrong; but if there’s a hit that’s annoyingly off, sure, go ahead and fix it.

The following relates to a technique I use a lot on nylon string (classical) guitar recordings, but which also applies to steel string guitar recordings in some cases. Classical guitar is an interesting instrument to record—part of that is because it has a rich vocabulary of artifacts, from fret buzzes to slides to fingernails scraping on the lower strings’ metal windings. In fact many samplers include samples of these sounds, which can be brought in by (typically) hitting a key harder or using a controller, to help create a more realistic emulation.

But for those times when the artifacts are a distraction rather than an enhancement, before the age of digital audio editing there wasn’t much you could do about the situation: It’s now possible to surgically remove, or at least reduce, many of these types of artifacts.

I first used this technique when working on a classical guitar album by an artist who had some health problems at the time. Most of his playing was exceptional, but occasionally some notes sounded “tentative.” I found that in those cases, there was some sort of sound preceding the note itself, and deleting that sound made the note ring through with authority. Since then, I’ve used this technique with other guitarists to reduce or remove artifacts that would spoil an otherwise perfect part. If you take this to an extreme, you can almost make a classical guitar sound like it was played by a robot with perfect technique—but I don’t recommend this any more than I recommend using Auto-Tune or Beat Detective on everything!

GATHER YOUR TOOLS

Doing this kind of editing requires a spectral view of the waveform (Fig. 1) so you can easily recognize the difference between the artifacts and the notes themselves, and perform the digital audio equivalent of a “window splice” in the frequency spectrum. I use Adobe Audition for this, although Steinberg Wavelab also gives an editable spectral view.

With Audition, call up the file and go View > Spectral Frequency Display. Adjust the resolution as desired, then look closely at the notes. Note attacks will have a sharp, vertical line that extends from low to high frequencies. Artifacts almost invariably appear just before the note attack. You can use any of Audition’s selection tools to define the artifacts as a selection; when you do, a level control appears. You can then use this to dial in the exact amount of attenuation.

Fig. 1: Note the artifacts, outlined in gray, in the upper waveform. In the lower waveform, these have been removed completely by using editing tools in Adobe Audition’s Spectral Frequency view (the vertical axis is frequency with the colors indicating amplitude, while the horizontal axis is time). For clarity, each selection has a white outline that indicates what was removed; note that only higher frequencies have been removed, and the decay of the note itself has been left intact.

Surprisingly, it’s often possible to remove the area completely and not be able to hear that it was removed. Sometimes, though, you’ll need to reduce the gain (by a few dB) rather than remove the section to retain a realistic sound, or if you want to leave a bit of the artifact sound but make it less obvious.

PRACTICE MAKES PERFECT

It takes a while to recognize what’s an artifact and what isn’t, and to determine the degree to which you can reduce it. Life is often about compromises, and this is no different; you’ll find problems you can’t fix, and conversely, you’ll be able to fix problems you thought were unfixable.

In any event, if you’re willing to take the time to do this kind of detailed editing, you can produce the most amazingly clean and clear nylon string guitar parts you’ve ever heard, and clean up steel string issues as well.