In this excerpt from Ableton's Learn Live series on Emit, a granular sample playback device, the tutorial demonstrates how to route Envelope 1 to an emitter's pitch using the Routing section. Playing a MIDI note triggers the envelope and causes the pitch to jump sharply upward.
From there, setting Sustain to zero and increasing the Decay time reshapes that pitch jump into a smooth downward glide, giving you a percussive pitch-drop effect tied directly to note input.