(hint #1) Being able to play whatever I want has been a central theme to my own discovering how to play guitar. I've been on that path for 37 years, and it's enabled me to uncover, test and refine a unique, skill generating learning approach.
It is important to note that urethane foam is most commonly used to refer to a material made from polyurethane. The urethane reference in this name is to the type of links, also known as carbamates, that join the units in polyurethane.
The use of the polyurethane and urethane terminology has largely emerged as a need to differentiate products that have varying performance. It is fact that the performance of polyurethanes can vary greatly depending on how the polyurethane is formed and the formulation of the finished product.