Zoom H4n Pro Operation Manual page 21

Front
Switch between track recording and playback.
When you start recording, press the track number you want to
record and the track becomes Recording Standby status. That
track button will then become illuminated.
Make track and the input source settings
After selecting the track, use the input source buttons to select
the input for that track. Using the INPUT button you can record
in mono, stereo or a combination of both.
Same for tracks 2-4
TRACK 1-4
Same for tracks 3 and 4
and 2
These are the four possible
input selections.
Note: These operations are not possible
during recording and playback.
These operations are not available during
recording and playback.
When tracks are stereo-linked, pressing the
on the linked track.
P.058
Stereo link
020