Every instrument should stake its own claim in the frequency spectrum. For example, bass and kick drum own the low end. So if the guitar has lots of low end, the bass and kick will mask the guitar sound, and the guitar’s low-frequency energy will “blur” the kick and bass. There’s an easy fix—add a low-cut filter. Many EQ plug-ins now offer steep low-cut slopes— like 48dB/octave—so cut mercilessly below 90Hz. The bass and kick will acquire more clarity, and the guitar sound will tighten.