Multisampling
Recording an instrument at many pitches and dynamics and spreading the recordings across the keyboard, instead of transposing a single note.
A sampler can play a recording higher or lower, just not very far: a piano note moved up an octave sounds wrong, because the body resonances move up with it. The fix is to record every third semitone, or every single note, and let each recording cover a zone of the keyboard in what is called a keymap.
The same thing happens vertically. A hard snare hit does not sound like a soft one turned up, so velocity chooses between several recorded layers. Add round robin and the numbers climb fast, which is why serious libraries for Kontakt weigh in at tens of gigabytes for a single grand piano.