Reverb
The persistence of sound in a space after the source stops, simulated digitally to add depth and a sense of place to recordings.
Reverb is what happens when sound bounces off the walls, ceiling, and floor of a real space and reaches your ears after the original source has stopped. In a tiled bathroom, that tail is bright and long. In a recording booth, it's nearly gone. In a cathedral, it can last six seconds and color every note. Recording engineers use reverb to put a dry studio sound into a believable space — or to invent a space that doesn't exist.
The main categories: room reverb is short and intimate, hall reverb is long and dramatic, plate reverb is dense and metallic (originally generated by a literal vibrating steel plate), spring reverb is twangy and bouncy (the surf guitar sound), and convolution reverb captures the acoustic fingerprint of a real space via an impulse response. Each has a use: a snare drum often gets short plate; a lead vocal often gets a longer hall or chamber.
Three knobs matter most: pre-delay (how long before the reverb starts, which separates the source from its tail), decay (how long the reverb lasts), and wet/dry mix (how much reverb vs source). On vocals, a 30–60 ms pre-delay keeps articulation crisp before the wash sets in. On snare, a 2–3 second hall under a tight gate can sound enormous without losing the attack.