Masking occurs when two tracks dwell in similar frequency ranges, and the common frequencies either fight or cancel each other, so that the sounds obscure one another. Two common culprits are bass guitar and kick drum, which we’ll use as our example. When you’re mixing kick and bass, it’s helpful to use complementary EQ to eliminate masking. For instance, if you boost the kick drum at 50Hz, reduce the bass at around 50Hz. If you cut the kick a little at 400Hz to get rid of a “boxy” sound, nudge the bass up a bit at 400Hz. This technique will be helpful whenever two instruments with similar frequency ranges are battling for attention in your mix.