Choose an instrument, from vocals and kick to 808, guitars, piano, strings, brass and synths, and the chart shows its important frequency bands on a real logarithmic scale from 20 Hz to 20 kHz. Hover or tap any band to read what it does (mud, boom, boxiness, presence, sibilance, air) and a sensible first move, or scroll to the table for a printable cheat sheet. The overview shows the classic sub, bass, low-mid, mid, upper-mid, presence and air ranges.
Mud usually builds up between about 200 and 500 Hz. Small cuts there on vocals, guitars, pads and piano clean up a crowded mix.
Vocal presence and clarity sit around 2 to 5 kHz. A gentle boost near 3 kHz helps lyrics cut through, while sibilance lives around 5 to 8 kHz.
The body and punch of most kicks is around 60 to 100 Hz, with the beater click around 2 to 5 kHz for small speakers.
Air is roughly 10 to 20 kHz. A high-shelf boost there adds openness and sheen to vocals, cymbals and full mixes.
Cut first to remove problems, then boost gently to add character. Cuts tend to sound more natural and leave more headroom.
No, they are starting points. Every voice, instrument and recording is different, so sweep around the range and trust your ears.