Are "be in tune with" and "understand" interchangeable in some situations?

Question

In my other post (the grammar rule of "against my hearing you"?) I said

If it was "against/prevent I hearing you", I would be in tune with the meaning.

I am aware that "be in tune with" means "having a good understanding" and I was trying to express

If it was "against/prevent I hearing you", I would understand the meaning clearly.

and I used "be in tune with" to convey that meaning.

Do they mean the same?

In other words, are "be in tune with" and "understand" interchangeable in this kind of situations?

Answer 1

"Be in tune with" has a somewhat different field of meaning than "understand."

I understand you but disagree

is idiomatic whereas

I am in tune with you but disagree

is not idiomatic.

I agree with your conclusion even though I don't understand your argument

is idiomatic as is

I am in tune with your conclusion even though I don't understand your argument.

In other words "in tune with" indicates agreement or sympathy without necessarily implying understanding. Of course, understanding is frequently associated with agreement or sympathy, and thus "in tune with" certainly does not imply a failure to understand.

Answer 2

When you are in tune with someone/something you have a good understanding of someone or something, meaning that you know how someone behaves or how something works. This refers to the fact that you understand them as a whole. In other words, it doesn't refer to a particular instance.

sometimes understand and be in tune with are interchangeable:

He is more in tune with his players today, because he has asked them for their opinions. (cambridge)

in the example above if you use understand the sentence still makes sense, but this isn't always the case as @Jeff Morrow mentioned in his examples.