Cutoff and resonance

A bassline plays through a low-pass filter. Drag Cutoff slowly from bottom to top while it plays.

Cutoff is the frequency where the filter starts cutting. Low, and only the deep part of the sound gets through: dark and muffled. High, and everything passes: bright and open. Sweeping the cutoff is one of the most used moves in electronic music.

Res (resonance) boosts the frequencies right at the cutoff. A little gives the sound an edge; a lot makes it whistle and squelch, especially while you move the cutoff.