Bus Processing

Glue and saturation can flatter AI material, but compressing an already flat mix only makes it flatter.

Related

BusCompressorParallel Compression

The problem

Bus compression and saturation are the two most addictive moves in mixing. Engaged, the mix immediately sounds like a record, drums tighter, vocal closer. AI material is already flat, so a compressor can only shave the little variation that remains while saturation fills the upper midrange. The result is not glue but dullness, pumping and lost transients.

How it works

Glue comes from shared gain reduction, which makes parts rise and fall together by a small amount and creates micro-dynamics. When the source has none, the compressor follows the loudest transient, lifting weak passages and pressing strong ones, so the mix reads flatter. Saturation adds harmonics, density and presence, but also raises indicated loudness, which flatters the ear. AI output often arrives after one round of limiting and saturation, so a second round is repeated processing, with harmonics piling up between 1 and 3 kHz.

Practice

Look at the meters first. Bypass the bus compressor and compare crest factor; a difference under 1 dB means it is colouring, not working. If you use it, try a 30 ms attack with auto or 200 to 400 ms release and keep gain reduction at 1 to 2 dB. Parallel compression is safer, placing the compressed signal under the clean one so transients survive. Put saturation only on drums or a high layer, blend 10 to 20 percent, and level-match every comparison. If the material is already flat, skip bus compression and spend the dynamics on volume automation instead of asking one plugin to revive a flat mix.

What to listen for

In the 65 BPM rock groove, hear whether kick and snare attacks survive; a slow attack should let them through. In Chopin's Ballade No. 1, hear whether the climb from soft to loud has been pressed into a straight line, since too much glue destroys that arc. In the organ hymn, hear that sustained chords have no transients to grab, so saturation only thickens the midrange. Level-match all three before deciding whether the plugin helped or merely got louder.

Sources

• 总线胶合与并联压缩的判断，依混音通识与听感实践核对，未抄文本
• Bus glue and parallel compression, based on general mixing practice, no text copied

Used for fact-checking only; all prose is original.