Ratio 2:1 for gentle bus glue, 4:1 is a starting point for individual parts, higher ratios for heavy control

There are loose conventions for ratio starting points. Gentle ratios (2:1 or lower) work well on mix buses or subgroups of instruments where the goal is cohesion without obvious effect. Around 4:1 is a conventional starting point when compressing individual tracks. Higher ratios are appropriate for parts requiring heavy dynamic control — lead vocals often need ratios of 6:1 to 10:1 or more. These are starting points, not rules: the correct ratio is always determined by ear against a reference mix, and harder compression is sometimes intentionally audible as an effect. The harder the compression, the more likely the compressor’s character (artifacts) will color the sound.

Examples

Start a drum bus with 2:1 ratio and a soft knee. Start a lead vocal with 4:1 and adjust up if dynamics are still unruly. If the vocal needs a limiting effect, push toward 10:1.

Assessment

What ratio range is appropriate for a full mix bus versus an individual vocal track? What happens sonically as ratio increases toward limiting?