Change keyboard hot keys

I have a friend who built a machine for making drum bodies. It functions similar to a lathe in that it has only an X and an A axis for carving the shell. Currently, using the keyboard, the LEFT and RIGHT arrow jog the X axis, and the [ and ] keys jog the A axis.

He would like to use the UP and DOWN arrows that are typically used for the Y axis to instead move the A axis.

How can he accomplish this?

EMAIL:

Years ago you helped me getting LinuxCNC dialed in on my DIY rotary CNC I used for making drums. I have a quick question:  Since my machine does not use the Y axis, I would like to have the up and down keyboard buttons control the rotary.  Using the "[" & "]" has never felt natural/intuitive for me.  Do you know if this would be an easy process (then I am interested), or is this a complex process (then it is not worth it).  If you could point me in the right direction, I would appreciate it.

I have seen some people have mention "USER_COMMAND_FILE", but I am not sure how it all fits together.  I am not ever sure if this is what I need (could be the wrong rabbit hole to go down for this). Thanks,Rob

Any help is appreciated.
Jerry