Apple Logic Pro X - Manual (Page 810)

Chapter 23 Work in the Environment 810
Monitor objects
A monitor object displays all events (MIDI and meta) passing through it. It remembers the last 32
events, with the newest events shown at the bottom of the list. You can resize it to show from 1
to 32 events. Clicking anywhere in the body of the monitor clears all events.
Monitors are useful as both testing and branching devices. When coupled with objects that have
functionally different outputs (channel splitters and mapped instruments, for example), monitor
objects can be used to attach more than one output cable to the same function.
Create a monitor object
m Choose New > Monitor.