The Basics of Audio Manipulation

Delay, EQ, & Compression

In this series of essays I attempt to distil down sound production and it’s associated methods to their simplest forms. Most effects can be broken down into simpler more basic parts, and those basic parts are then reconfigured into other effects.

For example, the famous Phaser effect, the wooshing of a jet plane sound, that is (essentially) the same effect as a Chorus effect (a sort of doubling and thickening effect) and a flanger effect. More on those later, back to the basics.

Most signal processing in the electronic music world consists of some sort of audio delay and feedback line, some filtering (low pass,high pass, simple EQ or simple sonic degradation from regeneration), compression aka dynamic processing, and lastly distortion. Distortion is essentially ‘errors’ in the signal path making it sound different, because, in this case, the data is the sound and the errors are the unintended added or removed sounds.

Building Blocks, Chapter One

Delay and Feedback

Understanding the basic concepts of delay and feedback are crucial to speedy production since most effects used in “the studio” (or DAW) are variations of this most simple and most often used feedback network.

Rhythmic Delay

• Basic Concept: It simply involves playing back an audio signal after a short period of time, and again, and again. Each time delayed by the set duration.
• Feedback: When the delayed signal is fed back into the delay input, it creates repeating echoes. The amount of feedback controls how many times the echo repeats.

Reverbs

Reverb algorithms come in a wide variety of configurations, but no matter if you are using a true analog bucket brigade guitar pedal or the latest convolution and algorithmic digital reverb plugin, a series of delays and filters will be involved in creating the final effect.

• Relation to Delay: Reverb can be thought of as a complex set of multiple, very short delays, each regenerating at a different rate, but working as a unified system. It simulates the natural reflections of sound in a physical space.
• Feedback: In artificial reverb, these delays are combined with varying feedback levels to create the sense of space and depth.

Chorus

That classic sound used on bass guitars in all genres, and on guitars in disco and other more ‘classic’ genres. Now-a-days the chorus sound is used with automation to self oscillate the feedback and pitch it around for some wild and easy-to-create sound effects, done in DAWs and and Modular systems

• Relation to Delay: A chorus effect uses a short delay along with slight variations in the delay time. This creates a doubling effect, as if multiple sources are playing the same sound with slight timing and pitch differences.
• Feedback: Feedback is typically subtle in chorus effects to maintain the natural feel.

Flanger

• Relation to Delay: Flanging is similar to chorus but uses an even shorter delay time. The delay time is modulated, which creates a distinctive swooshing or jet-like sound.
• Feedback: Flangers usually incorporate feedback, which intensifies the phase cancellation and constructive interference effects, creating a more pronounced effect.

Phaser

• Relation to Delay: A phaser splits the signal into two paths, with one path undergoing phase shift due to all-pass filters. While not a delay in the traditional sense, it relates to delay because the phase shift creates peaks and troughs in the frequency spectrum, similar to comb filtering (a result of short delays).
• Feedback: Feedback in phasers intensifies the peaks and troughs, making the effect more noticeable.

Pitch Shifter

• Relation to Delay: Some pitch shifters use delays to achieve the pitch-shifting effect. They play back the audio at different speeds to change the pitch, often combined with crossfading techniques to smooth the transition.
• Feedback: Feedback isn’t a typical feature in pitch shifters but could be used creatively for special effects.

Granular Synthesis

• Relation to Delay: Granular synthesis involves taking very short slices (grains) of sound and playing them back with various parameters like pitch, volume, and pan. It can be seen as a form of delay where the ‘delayed’ signal consists of these tiny grains of the original.
• Feedback: While not a traditional aspect of granular synthesis, feedback could be used creatively to feed grains back into the process, creating complex textures.

Feedback Management

• Importance: Managing feedback is crucial in all these effects. Too little feedback might make the effect too subtle, while too much can cause excessive repetition or even uncontrollable oscillation.
• Creative Use: Feedback isn’t just for control but can be a creative tool. Skilled manipulation of feedback can create unique textures and atmospheres in a mix.

In summary, many audio effects in mixing can be understood through the lens of delay and feedback. Each effect manipulates these basic principles in different ways to create a wide variety of sounds and textures used in music production. Understanding these fundamentals allows a mix engineer to use these tools more effectively and creatively.

Building Blocks Chapter Two : Equalization and Filtering

Understanding how equalization (EQ) and filters are related in audio engineering is fundamental. Let’s delve into this:

Basic Concept of EQ

A simple channel EQ, or a parametric one used in classic home stereo setups, they all have some very similar properties and controls. Understand one concept and you understand everything.

• Purpose: EQ is used to adjust the balance of frequency components in an audio signal.
• Mechanism: It works by boosting or cutting frequencies around a certain point (center frequency) to shape the tonal balance of the sound.

Types of EQ:

• Graphic EQ: Offers fixed frequency bands which can be boosted or cut.
• Parametric EQ: Provides more control, allowing you to adjust the center frequency, bandwidth (Q), and gain.

Filters as Selective EQ

• High-Pass/Low-Cut Filter: This filter removes frequencies below a certain point, allowing higher frequencies to ‘pass through.’ It’s like a very steep EQ cut below a certain frequency.
• Low-Pass/High-Cut Filter: Opposite of the high-pass, this removes frequencies above a certain threshold. It’s akin to a steep EQ cut above a certain frequency.
• Band-Pass Filter: Combines high-pass and low-pass, allowing only a certain band of frequencies to pass through. It’s as if you’re cutting both high and low extremes using EQ.
• Notch Filter: Targets a very narrow frequency range to cut or boost. It’s like a parametric EQ with a very high Q value, focusing on a tiny frequency band.

EQ and Filters in Practice

• Shaping Sound: EQ and filters are used to shape the sound by removing unwanted frequencies (like rumble or hiss) or emphasizing desired frequencies (like the warmth of a bass or the brightness of a vocal).
• Creating Space in a Mix: By EQing instruments differently, you can create space in a mix. For example, cutting low frequencies on non-bass instruments to leave room for the bass.
• Dynamic EQ and Filters: Some modern EQs and filters adjust their parameters based on the input signal, allowing for more precise and dynamic control.

Creative Uses

• Sweeping Filters: Automating the frequency of a low-pass or high-pass filter can create a sweeping effect, often used in electronic music.
• Surgical EQ: Using narrow notches to remove problematic frequencies or resonances.
• Tonality Adjustment: Using broader EQ adjustments to change the overall tonality of an instrument or a mix.

Technical Considerations

• Phase Shifts: Both EQ and filters can cause phase shifts in audio signals. Understanding how these shifts affect the sound is crucial, especially in a mix context.
• Resonance: Some filters add a resonance peak at the cutoff frequency, which can be used creatively for emphasizing certain frequencies.

Conclusion

In essence, filters can be thought of as highly specialized forms of EQ. They are both tools for manipulating the frequency content of audio signals, but filters tend to be more aggressive and focused in their application. Whether subtly adjusting the tonal balance with EQ or dramatically shaping the sound with filters, both are indispensable tools in the mix engineer’s arsenal. Understanding their similarities and differences is key to effective and creative mixing.

Building Blocks: ChapterThree

Compression and Dynamics

Dynamics processors, at their core, are variations of a basic compressor, each tailored for specific purposes and with unique attributes. Let’s break down how different dynamics processors, including the ones you mentioned like the Waves L1 Ultramaximizer and multiband compressors, are essentially based on the fundamental principles of compression.

Basic Compressor

• Function: A compressor reduces the dynamic range of an audio signal by lowering the volume of louder parts and optionally raising the volume of quieter parts.
• Key Parameters: Threshold (level above which compression occurs), Ratio (how much compression is applied), Attack (how quickly compression starts), Release (how quickly it stops), and Make-up Gain (to compensate for lost volume).

Variations of Compressors

Limiter (e.g., Waves L1 Ultramaximizer)

• Relation to Compressor: A limiter is essentially a compressor with a very high ratio, often considered as ∞:1. This means that once the signal exceeds the threshold, it is not allowed to get any louder.
• Specialty: Limiters are used to prevent audio from peaking above a certain level, making them essential in mastering to achieve loudness without clipping.

Multiband Compressor

• Relation to Compressor: A multiband compressor divides the frequency spectrum into multiple bands, and a separate compressor works on each band. This allows for more targeted dynamic control.
• Use: It’s particularly useful for complex material like a full mix, where you might want to compress the bass differently from the treble.

Maximizers

• Relation to Compressor: Maximizers are advanced limiters designed to increase the overall level of a mix while controlling peaks. They often include lookahead functions and other sophisticated algorithms.
• Goal: The goal is to make the music as loud as possible without introducing distortion or other undesirable artifacts.

Other Dynamics Processors

• Expander/Gate: These are the opposites of compressors. Expanders increase the dynamic range, making quiet sounds quieter, often used to reduce background noise or increase dynamic impact.
• De-esser: A specialized compressor that targets sibilant frequencies (usually high frequencies) to reduce harshness in vocals.

Common Features

• Threshold and Ratio: These are fundamental parameters in all these processors.
• Attack and Release: They determine how these processors react to the incoming signal.
• Knee: Some have a ‘knee’ control, which dictates how gradually or abruptly compression begins.

Application and Usage

• Mixing and Mastering: These processors are used extensively in both mixing and mastering. While mixing, they help in balancing levels and controlling dynamics; in mastering, they are used to achieve a consistent and commercially viable loudness level.
• Creative Effects: Beyond their utilitarian purposes, they can also be used creatively, such as side-chain compression for a ‘pumping’ effect in electronic music.

Conclusion

In summary, while all these processors — limiters, multiband compressors, maximizers, expanders, gates, de-essers — have unique characteristics and applications, they are all fundamentally based on the principle of compression. Understanding this core concept allows you to grasp how each processor affects the dynamics of audio and how to use them effectively in different situations in music production.