Have you ever had the experience of working on a mix, and while the balance is generally working, a couple of instruments seem to be clashing or covering each other up? This could be related to a psychoacoustic phenomenon known as auditory masking. Masking occurs when one signal distracts the ear from another signal happening around the same time.
Mixing kick and bass
A classic example of this comes when trying to figure out the relationship between a kick drum and a bass part in a mix. You might listen to them individually and find they sound big, full, and loud on their own, but when you listen to them together, the kick drum seems to get lost. You might turn the bass down so you can hear the kick drum again, but then the bottom falls out of the mix and the bass doesn’t have the power it needs to anchor the rest of the harmony. Countless engineers have spent hours trying to solve problems like these, but a quick understanding of how masking works can help you identify some solutions and start creating better-sounding mixes right away!
EQing bass and kick to relieve masking
One of the reasons bass tracks especially mask kick drums is because they both are competing for the low end of the mix. A kick drum is going to have some substantially high-mid frequency attack that helps it sit on top of a mix, but how do you get that satisfying thump in your chest with the kick drum, without sacrificing the sound of the bass?
One answer may lie in complimentary equalization. This is a simple process of identifying which frequencies collide between the kick and bass, and then boosting those frequencies slightly in the kick, while making a complimentary cut to those same frequencies in the bass. In the illustration below, we see the EQ for the kick drum on the left, and for the bass on the right.