Continuing with a topic discussed the other day, we are going to take a look at how we can harmonize a melody using these fourth structures.
First, start off with a melody:

Then, add the diatonic fourth below the melody (this can either be a P4 or a tritone):

Now, we are going to do a closed fourth voicing, which means that we will add a third below the melody note. However, for the harmony that has a tritone, we are going to add a third ABOVE the bottom note:

If we instead wanted to do open fourths, we would need to stack two intervals of a fourth on top of each other. So, that simply means adding another fourth below the fourth from the previous example:

But, notice how the one with X’s have a tritone in them. Technically, that does not exactly fit the definition of an open fourth structure. To edit this, we use chromatics to adjust the harmonic intervals:

And there you go!
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