First of all, song form is an indepentent concept from the boxes, boxes simply describe the way the ideas move.
But when we create a song, we generally create it in sections. And it's been convenient over the decades, over the centuries, to come up with names for the various segments, that various sections, that you divide a song into.And those sections are generally put together in terms of what job they have to do. What is the function of the various sections? And so, we have this section called verse.
Verse:Delivers the basic informations of your song.
The basic job of the verse is to give us the fundamental story or the fundemental feeling, this sort of platform that the song evolves from. So that the function of the verses is to just give the basic informations, and then we have this chorus idea.
Chorus:States the central idea of the song,moves to a different level and summarizes and/or comments on the information delivered by the verses.
The chorus is the thing, when there are choruses in a song, that you'll repeat, over and over again. And because you're repeating it, twice, three times, it's important that chorus be able to grow. That chorus state the central idea of your song, and that it be able to take on whatever information your verses are giving it. The chorus doesn't typically advance the plot. The chorus doesn't typically change its words.It is a reiteration of the central idea of the song as we move forward, so that's verse,that's chorus.
Bridge:Connects song sections, also moves to a different level of information than the other sections.
And then we have this thing called a bridge, and the bridge again, moves to a different level of reality. Nobody lives on the bridge, the bridges job is to take you from Brooklyn to Manhattan, or from Manhattan to Brooklyn. People may live under the bridge, but they don't live on the bridge. So that the bridge is something that moves you from landmass to another, so it also happens on a different level of reality.
Pre-chorus:Links between verse and chorus.
And, by the way, this pre-chorus, is actually just a little bridge that goes from verse to chorus, and we'll see some examples of that.
I will refer you to some examples of that, but that's basically what happens inside the boxes as you start putting the sections of your song together. And the sections fit inside the boxes, and again, it's a very flexible thing. That is to say, any, the first box could easily contain simply one verse and one chorus, second box, one verse and one chorus, and that may be the entire song. If you have a third box, maybe now you're going to switch-up and have bridge, chorus, so that you'll enter the chorus from a different angle.
So that's very quick and easy song form.