In any room, sound reaches the ear directly and then again after bouncing off walls, floor and ceiling. A group of distinct early reflections arrives first, followed by a thick, noise-like tail that gradually dies away; together they make up reverberation. Their timing tells the ear whether a sound is in a small booth, a club or a cathedral, and the delay before the reverb arrives is a strong clue to the size of the space. Today most artificial reverb is created digitally.
Reverb gives jazz lo-fi much of its sense of place and depth. A short room on the drums can suggest a small jazz club, while a long, dark tail on Rhodes chords creates a dreamy, nocturnal mood. Too much, though, blurs the mix and pushes instruments into the distance.