Quantization (MIDI)
Snapping recorded notes to the nearest line of a time grid, so slightly loose playing lands exactly on the beat.
It only works because the music is stored as events rather than sound. A MIDI note has a start time, and that can change without anything sounding different. Hard quantising to sixteenths gives a machine precision that suits electronic music perfectly and kills most other kinds. So every sequencer has a strength setting that moves notes only part of the way, and a window that leaves notes already close to the grid alone.
Swing is quantisation's opposite: every other subdivision is deliberately pushed late. Roger Linn's drum machines around 1980 had both quantise and swing, and his swing percentages on the Akai MPC became a sound of their own in hip-hop. Groove quantise goes a step further and copies the timing profile of an actual drummer.