If you’re confused (given that you care at all) about the difference between blank verse and free verse, here’s the thing:
Blank verse was an invention on the way to free verse; i.e., Blank verse is so many lines of iambic pentameter. Free verse doesn’t give a (BLEEP) about the type of feet in a line, and really doesn’t care about the number of feet in a line, either (although some free verse sticks to five feet per line.
Just so you’ll know, a line such as this old chestnut:
“In Xanadu did Kublai Khan” consists of four iambs (feet). If you were to diagram it according to stresses, with “^” indicating a strong emphasis and “-” indicating a lesser stress that line could be diagrammed thusly: – ^ – ^ – ^ – ^ or if this doesn’t make sense, (I’ll capitalize the most emphasized syllables): “in XAN a DU did KU blai KHAN”
But there are other types of feet (impress your English prof with these – and they have names!):
Feet of two syllables:
Iamb – ^ de LIGHT
Trochee ^ -SPLEN did
Spondee ^ ^ DROP DEAD!
Feet of three syllables
Anapest – – ^ in ter TWINE
Dactyl ^ – – SPLEN did ly
Amphibrach – ^ – de LIGHT ful
Feet of four syllables
1st Paeon ^ – – – NOT ed is a
2nd Paeon – ^ – – de LIGHT ful ly
3rd Paeon – – ^ – in the TWI light
4th Paeon – – – ^ out of the OAK
Okay, big deal, right? These fancy feet look like a combination of the simpler, shorter feet. Right?
But here’s a subtle thing that can mean a lot when it comes to stretching iambic pentameter. Let’s suppose you had a combination of some of these example words and phrases above.
Splendid doesn’t mean delight
And as we sit here in the twilight…
We might diagram these with stresses thusly, according to our names feet:
^ – ^ – ^ – ^ SPLEN did DOES n’t MEAN de LIGHT
– ^ – ^ – – – ^ – and AS we SIT here in the TWI light…
But read that last line aloud: when you get to the word “in” the temptation is to stress it as “IN,”
– ^ – ^ – ^ – ^ – and AS we SIT here IN the TWI light
What you’re doing there is changing the rhythm when you get to “…in the twilight…” but something in you – and in the reader’s ear – makes you want to keep accenting as if this were a string of iambs, but ending with a “feminine” or unaccented syllable. This is the way we in modern free verse make music with our words. Being aware of this, you can make the music!