This Ableton tutorial demonstrates two Max for Live devices on a Bass track: Expression Control, a MIDI effect, and an LFO modulation device. Both share the same core mechanic: clicking Map lets you route the device's output to any parameter visible in Live's interface, whether that's a filter, a mixer control, or even a parameter on a completely different track.
Expression Control is mapped here to the track's filter cutoff, letting any selected MIDI expression source drive that parameter in real time. The LFO is mapped to the track's mixer volume, creating automatic level modulation without any automation drawn in.
The key takeaway is that the Map button in both devices is universal: you're not limited to the device's own parameters or even its own track. That flexibility makes Max for Live modulation tools significantly more powerful than standard MIDI routing in Live.