The Mesostic, invented and developed by composer John Cage, combines chance and choice operations.
The rules are simple and intriguing, something like an acrostic, but slightly more complicated.
Choose a word, such as CHANCE. This word becomes the spine of your poem:
Now, create a series of words that enfold these letters. You can do this either with single words or with phrases, but the single words are the most challenging and intriguing. The other simple rule is that the spine letters cannot appear in the words between them. So:
is OK, but
is not properly a mesostic by Cage's rules, because C occurs again between the capital C and H letters of the spine. This makes a mesostic with the word "chance" tricky, as one cannot follow the C with the H until after H is used, or follow an A with and N before the N is used.
Writing a Mesostic heightens one's awareness of the operations of language restrictions as they intersect with chance. At one point there was a Mesostic generator online, but it is no longer operating. Perhaps another will arise. Meanwhile, if you want to write one, you'll need to deal with the raw material of language itself. Most Mesostics keep the parts of speech parallel (a list of nouns works especially well), but that's not Cage's rule. I'm in love with verbs, so I find a list of nouns challenging.
Here's my warm-up attempt at a Mesostic sentence:
Here's my attempt at a Mesostic poem of nouns:
You can see that the non-sentence offers the reader far more possibilities for justaposition and interpretation. That's one of my choice take-aways from this "chance" experiment, enhanced by restrictions.
Here's a tribute to Cage and the Mesostic by Michael Carlson, that displays his own mesostic experiments. His Mesostic mesostic is brilliant, and uses a series of nouns.
Here's a blog post from Archie Wah Wah with some 50% mesostics, meaning that they don't follow the rule about repeated letters between words. This may be the easiest way to start, unless you want to plunge into the advanced challenge first. These are also sentence Mesostics.
Finally, a wonderful essay by Marjorie Perloff on Cage's Mesostics that describes his process in developing the form.