Working with Virtual Guitars.
I have been experimenting with a lot of virtual plugins for electric guitar. When I lived in an apartment in the city, there was a noise ordinance in place, so I could not play my instruments very loud. In music production, distorted electric guitars provide a rich texture to a mix. Distorted guitars also provide an interesting sample for those interested in subtractive or granular synthesis for electronic dance music (EDM). But working with guitars in a virtual environment sometimes misrepresents the natural sound of an electric guitar.
Let's look at why the guitar is such a unique instrument and sounds so good through an amplifier.
Feedback
The interaction between guitar, floor and microphone.
The most considerable interaction we see with the electric guitar and amplifier system is the inherent feedback loop. The pickups amplify the sound produced by the metal strings, then feed down the guitar cable into the amplifier, creating a much higher SPL into the room. This sound hits the guitar strings again and sympathetically vibrates them, causing the sound to be picked up again by the pickups. This feedback is very apparent in the traditional metal guitarist holding their guitar up to an amplifier to get the system to feedback. The small feedback loops at higher frequency levels contribute to the guitar's overall sound even when far away. These small feedback loops don't exist with an electric guitar plugged directly into a computer or tablet or using a virtual instrument to produce amplifier tones.
Recording
When recording, the interaction of the guitar and the amplifier and the floor produce some intriguing reflections and feedback options. As Alex Case stated in an AES journal entry, the interaction with the floor and vs. the direct sound from the amp produces a comb-filtering effect that can either aid or hamper the recording process. So, we can use this interaction to be part of the tone, or we can try to reduce the interaction by adding carpeting, raising the amp, or reducing the mic's distance from the amplifier.
Least Significant Bit
The other issue with virtual amplifiers is the problem of the quantization effect of the least significant bit. Think about it this way; you have a light dimmer; more light comes into the room as you turn the dimmer up. This is analog. In digital, you have to flip the light switch many times a second to get the light to be in the room continuously. In a digital recording system, we must worry about what happens at the 0 to 1 Bit portion of the bit depth plot. When the audio signal dips below the 2 and 1 bits because it reduces volume, the computer remembers acts as 1's and 0's, electricity on or off. At 1 bit, it still thinks this audio is "on," but below the 1 bit, in analog, there are many decimals for the audio to hang out at before it goes to nothing. It is an electrical limbo in digital land, and the computer is not sure what to do with it. We get a quantization error. To overcome this, we put a virtual noise floor called Dither into the 0-1 bit depth, so technically, the computer is always quantizing and sampling; it never stops and shuts off the light switch.
But in recording the guitar, the natural interaction of the amplifier, which might make those last notes ring out a lot more, would be cut off by this quantization error and reduce the signal below the dither protocol. Thus we might have reverb tails end quicker and less natural.
What can you do?
How do we make those virtual guitars sound more natural? There are a couple of steps we can take.
1) Add a slight delay with 50-70% feedback to the guitar to extend those big, long, drawn-out notes. This delay will help the virtual plugin handle the LSB (Least significant bit) and extend your distortion or FX times to a more natural sound
2) Add reverb pre-virtual plugin. This tip doesn't apply to fast runs, but for those long, drawn-out notes and chords, it sure will. Automate the reverb in so it only pops in during the parts you struggle with keeping the guitar sustained.
In the end, we use virtual instruments for several reasons; we live in apartments and can't make loud noises, we want to change the tone of a sound, we don't know how to play the guitar, so we use an instrument we can play and try to make it sound like a guitar. However, nothing can replace a well-played guitar, but if we think about the specifics of what makes it such an incredible instrument, then we can sure try to get close.
