Compression is one of the most fundamental tools in audio mixing, and, in the most basic terms, is used to control the dynamic range of a sound or a mix. Dynamic range refers to the difference between the softest and loudest parts of a recording. But, controlling the dynamic range in a variety of ways offers a whole world of sound shaping power, all thanks to one of the most vital pieces of gear a studio has in their arsenal. Here’s how compression is typically used:
Leveling: Compression is used to even out the levels of different elements in a mix. It reduces the volume of louder parts (above a set threshold) while leaving softer parts unaffected, making the overall sound more balanced.
Sustain Control: Compression can be used to control the sustain or decay of a sound. By adjusting the attack and release settings on a compressor, an engineer can shape the envelope of a sound, making it punchier or smoother.
Transient Shaping: Compression can affect the transients of a sound. By adjusting the attack time, an engineer can either emphasize or reduce the initial impact or attack of a sound.
Gluing the Mix: Compression can help “glue” the mix together, making it sound more cohesive and controlled. This is often achieved by applying a subtle amount of compression across the entire mix.
Preventing Clipping: Compression can help prevent peaks from going above a certain level, avoiding distortion or clipping in the signal.
Creative Effects: Engineers sometimes use compression creatively, intentionally exaggerating its effects to create a specific sound or texture.
Parallel Compression: Blending a compressed signal with the original dry audio can help maintain dynamic range while providing the punchiness and control imbued by the compressor.
As you can see, compression is not just a one-trick pony, and can be used in a variety of ways to shape a recorded audio signal.