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Creatively Manipulating Guitar DI

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With the need for modern productions to be increasingly original, going back to basics in a unique way can often yield pretty inspiring results. Here we're going to take a look at a basic guitar part. We'll manipulate the source audio in a way that befits modern productions and, in turn, provides the opportunity for you to experiment with the ideas discussed, with the aim to help you take your future productions in a different direction.

1. Recording the DI

Direct injection (commonly known as "DI") is the process of recording the source instrument (in our case, electric guitar) directly, without the need for an amp or similar. Capturing this particularly raw signal, right at the start of a long processing chain, is exactly what this tutorial is based upon. Once we have the DI signal we can then decide what to do with the audio itself.

Manipulating the audio at this part of the chain can bring a new side to creativity to the audio processing in your production. This is because we are adjusting, twisting, changing the audio before it hits any kind of amplifier or plugin. This is particularly unique as we are changing the performance itself and channeling that into any post-production we do. So in this case, it's almost as if the manipulation is the performance.

Note: Pro Tools is used in this tutorial however all these steps are easily replicated in any major DAW.

Here is a straight forward guitar part we'll start to process. This is the raw, basic, DI part - no frills:


In this instance, I have "re-amped" the part using the free Sans-Amp plugin, with comes bundled with my package of Pro Tools.

The idea behind most DI processing is for exactly this purpose; you can re-amp the original sound, creating a variety of sounds to chose from when it comes to the mix.

So here is the DI part, now re-amped:

Re-amping... for Real

If you have access to a sufficient output and an amplifier, you can send this signal to a piece of equipment of your choice and re-mic, and record the signal back into your DAW. This is where the process usually stops when traditionally processing DI. And this is where we begin.

You can get particularly creative here!

With the performance already captured you can, for example, now go to your amplifier and adjust the gain whilst the DI part is being played. Why don't you play with EQ as the part progresses? Or perhaps you could even hold the microphone itself and move around the room whilst the part is played back, to create a particularly chaotic sound. 

Now that you don't have to worry about playing the part, you can be adventurous and get results no one has heard before.

2. Quantizing

One of the more obvious ways we can manipulate audio is to quantize it. In other words, put the performance in time.

Quantizing (put simply, putting a performance in time) is a fairly easy process for MIDI-based recording, but audio can often be much trickier. If you mic a guitar amp up and then try to put the audio in time, you create many issues. However, if you quantize the DI part, you are attacking the timing before it hits the amplifier or plugin.

Obviously, there is no substitution for a good, solid performance, but this might be a good solution if either your guitarist cannot make another session or you want to be particularly creative and stretch the timing in ways it's not physically possible to capture.

In Pro Tools this is a fairly easy process.

First, change your track view to Warp mode and select Polyphonic from the Elastic Audio part of the channel view, as below:


Above: The track has been put into "Warp" mode and set to "Polyphonic" for quantizing purposes.

Once you have done this, the waveform view (on the right hand side) will display the hit points—these are the grey vertical lines and it is these points that will be quantized.

Select the recorded region and open up the Quantize window (Alt+0), as below:

The Quantize window in Pro Tools offers us the ability to set the parameters of which the time manipulation will snap to.

I have selected 1/16 notes as my quantize grid (given the nature of the performance) and then click "Apply".

You will end up with the audio now quantized and snapped to the grid, as per the view below:

The audio has been quantized and snapped to the grid, as you can see above.

You may need to fine tune the placement, the software can only go so far at 'guessing', but in this case Pro Tools worked it out perfectly and as you can see, all the hit points within the waveform are now lined perfectly with the grid.

This is how our audio now sounds:


We now have a completely in-time guitar part, corrected at the stage before the guitar signal actually hits the amplifier or similar.

So now let's re-amp the newly quantized audio, for the finished product:


We now have a guitar part that is fully in time with the backing track and has been fixed as close to the original source as possible. This means the amplifier/plugin/etc can do it's job without needing to be quantized as well.

3. WAV Editing

Let's now get really creative and play around with the audio itself.

We'll look at three ways we can change the audio we've captured - 1) chopping, 2) a tape-stop effect and 3) reversing. These are by no means comprehensive, but are three easy ways to get your creative juices flowing and give you ideas of your own to experiment with.

"Chopping"

First, let's look at a very simple process called "chopping", where we copy and paste repeated parts of a guitar part for effect.

To begin, this is a chord sequence that fits with the picking part:


It's been re-amped but I want to do something different with the part.

Above: There are now three tracks in the project; the original picked part which has now been quantized; the chord part; and the duplicated chord part that has now been chopped.

As you can see above, I have duplicated the track which contains the guitar chords and copy + pasted various chords to create a "chopping" effect.

Here is the part, now chopped into WAV slices:


We have manipulated this audio by using the DI signal, not using the amplifier. This means from this point onwards, we can do all-sorts to the signal processing which would have been different otherwise. Although this example is basic, you can now begin to take this way further with your own ideas.

Now your DI has been chopped, why not place a mic in a large room and re-amp to capture all the natural reverb? You can the ambiance of the room as well as the chopped guitar part. This is just one example. The opportunities to create something original and unique to you are endless.

Tape Stop

Selecting the final part of our chopped DI guitar part, we're going to create a "tape-stop"-type effect. In Pro Tools, we'll use the bundled Vari-Fy AudioSuite plugin to achieve this.

Simply go to the AudioSuite menu and select the plugin - the basic settings work fine in this instance - and click Render.

See the box below:

Once rendered, the results sound like this:


Now let's put this in with the original picked part.

Here's how it's shaping up:


You can be a lot more creative than this but these basic ideas have already transformed a fairly straightforward part into something that sounds slightly different than what might have been initially expected.

Reverse

We're now going to take a slightly different approach to processing the DI signal. Although basic, this kind of processing is a little more experimental and can yield interesting results.

Reversing our DI signal is fairly straight forward. Again in Pro Tools, using the "AudioSuite" menu, simply hit the Reverse option to create a backwards version of your recording.

Here is the clean DI signal of the original picked part, now reversed:


The possibilities are endless. Why not use the sustained part as a transitional effect, for example?

Let's now re-amp the reversed DI signal:


This also sounds pretty interesting. However, to take this slightly further,  we'll mix this in with the original DI signal. (It is particularly common to mix both signals together, particularly with bass guitar, blending them to sit nicely within a mix.)

Here is the DI signal, and the re-amped signal, of the reversed effect:


Now you've got a pretty interesting starting point for creating a guitar part completely unique to you.

Conclusion

Recording the DI signal of an electric guitar and re-amping is nothing new—producers and recording engineers have been doing this for many years with great success.

However, interpreting the DI signal before it hits any kind of processing is almost unchartered territory and can help you create an original sound. By using these basic techniques you can begin to create your own unique ways of manipulating sounds.

If you've had any success with any of these techniques, or have any you'd like to share, let me know in the comments section below.

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