Tony Maserati relies on EQ, filtering and compression to fit a synth bass into the mix.
His goal is to ensure the synth bass complements, rather than competes with, the main bass and other elements in the mix.
He puts EQ before compression, carving out frequencies that clash with the main bass and kick, while enhancing frequencies around 50-60Hz. This low-end boost influences the compression action, creating a sidechain-like effect.