'O', 'oh': interjections and our English Bible translations

In my work with the Psalms I've noticed a peculiarity in several contemporary English translations. In the King James Version of the Bible, we read the following:

O come, let us sing unto the Lord:
let us make a joyful noise to the rock of our salvation (Psalm 95:1).

But in the English Standard Version we read this:

Oh come, let us sing to the Lord;
let us make a joyful noise to the rock of our salvation!

And in the New King James Version this:

Oh come, let us sing to the Lord!
Let us shout joyfully to the Rock of our salvation.

What the more recent translators appear not to understand is the difference between two words which we pronounce identically, namely, O and oh. The first word, O, is always spelled with a capital letter and is known as the vocative O. It is a somewhat archaic direct form of address used in poetry and older literary works. It sometimes comes before God's name in the Psalms, as in "O Lord" or 'O God," but not necessarily.

The word oh, on the other hand, is a multi-use expression running the range from mild surprise to a noncommittal response to a statement indicating only that the first speaker has been heard. For example:

"There is a raccoon in our back garden."
"Oh."

Whenever I would call my mother, she would answer the phone and immediately say, "Oh, hi!", as if she hadn't expected to hear from me even though she knew I'd be calling. But whatever oh means, it is not the same as the vocative O, which is lost on the translators of several modern Bible versions.

That said, I am not inclined to make too much of this, because I am given to understand that the vocative O is not found in the Hebrew text but seems to be a convention that the early translators imported, apparently for the sake of clarity. Modern translations could easily leave it out altogether, but they haven't. Oh, well.