We still use the subjective in many places in standard English. Certain constructions that traditionally use the subjunctive sound wrong and uneducated to me if an indicative is used instead. That having been said, there are people who never would use a subjunctive in some of the standard places where subjunctives show up.

Standard subjunctive uses: (With what some people would say instead in parenthesis)

I insist that he be fired. (I insist that you fire him.)

I wish I were rich. (I wish I was rich.)

If only this soil in my garden weren't so damn hard. (I wish this damn dirt wasn't so hard.)

God help us!

God bless America!

God save the queen!

If it weren't raining, we could have a picnic. (If it wasn't raining, we could have a picnic.)

It falls in a very broad area. Like many examples of slightly outdated English, we understand it effortlessly, it doesn't sound strange, but we would be unlikely to say it in everyday speech today.

Of course, it is hard to imagine expressing such a line of high drama using everyday speech. It is hard to make a small change that will make it sound "modern," because using the word "tongue" to mean "the thing we speak with" also falls in the category of "things we understand but rarely say." The first things that come to mind are:

"Murder always speaks, even though it has no mouth."

"Murder, despite having no mouth, will speak."

Of course, we could say

"Murder, though it has no tongue, will speak."

The phrase "It might have been..." sounds completely natural to me; unfortunately, I'm not sure whether or not that is an example of the subjunctive!

P.S. I'm learning Spanish myself. Unfortunately, using the English subjunctive to explain the Spanish subjunctive is useless, because it is rare in English; when we do use it, we do it intuitively and do not notice what we are doing; and it is hardly ever mentioned in school.

Not so strange at all, the meaning has not been lost to modern English speakers, especially to Modern English speakers of more than about 60 years old, because they would likely have heard similar speech from their grandparents. Modern English technically and academically began at about shakespeare's time

400 years ago, the phrasing is just reflecting how fast or how slowly the language is changing. 400 x 3 = 1,200 years a time span at which we know languages change to become unintelligible to modern or current speakers. 400 years is not quite long enough for the language to have changed from being understood or being effectively another forgotten language.

A playwright of today would phrase the line very similarly for dramatic effect.

For daily street speaking in current English the line becomes much too long and looses its effect.

"Murder, though (now you have to put in a convoluted explanation) ,will speak.

It is still the same today as it was then at the beginning of Modern English.

"Murder, though X will Y.

Thanks for your replies! Mr. Smith i invite you to have a Spanish lesson with me! I want to share to articles i found about subjunctive in old and middle english:

Thanks for your reply John! Still many of my students say they find this sentence strange to their ears. They are mainly from USA so maybe that's the reason. I got another example. "Whoever he be, he will have to pay for his deeds". Isn't "whoever he is" the usual form today? I bring this up because in Spanish we still use subjunctive in daily life and i try to explain it's uses to my students.