A problem like morphophonology

A problem like morphophonology
(sung to How do you solve a problem like Maria? from The Sound of Music)

It might look like any morpheme but then change the root, you see
It can lenite, subtract, or mutate and the morpheme is not free
It can even copy pieces from the stem too, if need be
It isn't quite a part of the morphology!

It has alternations looking like some well-regarded rules
Were it general we'd analyze with well-respected tools
But once we see it's limited it means we're all just fools
It isn't just a part of the phonology!

But you'd be mistaken if you believed we're outdone.
It's actually... quite some fun.

How do you solve a problem like morphonology?
How do you catch a morph and pin it down?
How do you solve a problem like morphonology?
Can vowel deletion derive a noun?

Many a time you think it's in the lexicon.
Many a morph you might misunderstand
But how do you pin it down, and account for all the sounds
How do get the pointing little hand?

Oh, how do you solve a problem like morphophonology?
How do you hold a morpheme in your hand?