Explain the technical differences between various audio compression techniques and their suitability in the context of EDM production including their specific parameters and how those parameters affect the sound.

Audio compression is a fundamental technique in EDM production, and understanding the technical differences between various compression types, along with their specific parameters, is key to effectively shaping the dynamics and overall sound. Compression, at its core, reduces the dynamic range of an audio signal, making the louder parts quieter and the quieter parts louder, which helps to make tracks sound more consistent, powerful and punchy. However, different compression types accomplish this in their own ways, resulting in distinct sonic characteristics.

One of the most common types of compression is VCA (Voltage Controlled Amplifier) compression. This type of compressor generally offers a clean and transparent sound with a more linear response, making it suitable for general-purpose dynamic control. The parameters associated with VCA compression are typically:
- Threshold: This parameter sets the level at which the compressor begins to engage. Signals exceeding the threshold are compressed.
- Ratio: This parameter determines the amount of gain reduction applied. For example, a 4:1 ratio means that for every 4dB of signal exceeding the threshold, only 1dB is allowed through.
- Attack: This parameter controls how quickly the compressor begins to compress the signal. A fast attack will clamp down quickly, while a slow attack allows more of the initial transient to pass through.
- Release: This parameter determines how quickly the compressor stops compressing after the signal falls below the threshold. A fast release will return the signal to normal quickly, while a slow release will maintain the gain reduction longer.
- Make-up Gain: This parameter is often used to increase the signal back to a usable level because compression reduces the level, and some compressors do it automatically.

VCA compressors are often used on drum buses and other instruments where you want a punchy and controlled sound without adding too much coloration. For example, a VCA compressor on a drum bus with a relatively slow attack to preserve the initial transient of the drums, a medium ratio for overall glue and cohesion and a medium-fast release to match the rhythm of the track, would make the track punchy and controlled.

Another type of compression is Optical compression. Optical compressors use a light source and a light-sensitive sensor to control the gain reduction. They are known for a smoother and more musical response, often described as "warm" or "gentle." This compression typically introduces a gentle curve, making it well-suited for vocals, bass guitars, and other instruments where a smooth compression curve is desired. Optical compressors have similar parameters to VCA compressors, but with a characteristically slower and smoother compression. An example of how to use it would be on a vocal, using a medium attack to let the initial transients through, a moderate ratio for dynamic control, and a medium-to-slow release for smoother sound.

FET (Field Effect Transistor) compressors are known for their fast attack and aggressive sound, making them suitable for drums, bass, and other percussive instruments where you need a more aggressive feel. They tend to add some coloration, harmonics, and saturation, which can enhance the track's character and presence. FET compressors have parameters similar to VCAs, but are often employed with a faster attack to catch transients quickly, a moderate-to-high ratio to add some punch, and a medium-fast release, and are great to make the sound more aggressive. For example, a snare might benefit from an FET compressor with a fast attack, high ratio and fast release that would help give it more attack and presence.

Vari-mu compressors use tubes to provide compression and have a very smooth, musical, and warm sound with high harmonic content. They are known for introducing harmonic distortion and have a natural compression character, making them suitable for mastering and bussing. Vari-mu compressors tend to add a lot of character to the audio signal, often using slower attacks and releases, gentle curves and often with automatic make up gain. Vari-mu compressors are often used on the master bus, with a very slow attack and release with a low ratio for glue and cohesion to achieve a polished sound.

Digital compression introduces many different styles with digital compressors that try to emulate some of the hardware options above and new techniques that are not available in the hardware realm. Digital compression can achieve very precise and surgical dynamic control and has the added benefit of lookahead, which allows for extremely fast attacks without missing initial transients and can help with more precise dynamic shaping. Also, modern digital compressors often have many added features that make them extremely flexible and useful. The same parameters apply as before, but the precision of the attack and release times are much higher, along with added features for side chaining or parallel compression.

The application of the different compressors will vary on the source material, and the results you're going for. Understanding the unique characters of the different kinds of compression, along with their settings will allow you to make your tracks more punchy, exciting, and dynamic in the mix. Knowing which type to use on a specific source will help give you the sound that you have in mind, while understanding their effects on the frequency content and harmonic character of your audio will give you more control and precision over your sound.