Form is a straitjacket in the way that a straitjacket was a straitjacket for Houdini.
Muldoon here was talking about poetic form, but the concept works across many (all?) creative endeavors. Houdini saw a straightjacket as an opportunity to come up with a new trick, technique, or way of working. It might have made him physically constrained, but it freed his creativity and pointed him in new directions.
In this series I wanted to see if I could create a coherent series of collages using only three elements each. I couldn’t turn to complexity to create interest. I couldn’t play with dozens of different allusions in one work. Three elements only.
It worked (though one has four).