This short Ableton tutorial covers two sets of controls in Emit that shape how grains play back: sample region settings and particle physics parameters. The host demonstrates how Length trims how much of the sample plays, while the start position lets you scrub through and select a specific region, with the spectrogram highlighting exactly what's being played.
Force controls how hard each particle is flung, extending how far it travels. Friction slows particles as they move, and the global Speed control scales the entire physics simulation at once. One thing to note: Speed also affects the Rate and Lifetime parameters, so it's a broader adjustment than it might first appear.