So, let's talk about the anticipatory set. (Big word; simple concept!)

Teaching is more effective when learners are excited about what they are learning. Generating interest and excitement for a lesson is the job of the anticipatory set.

It is like whetting the class' appetite for the "meal" of learning. The anticipatory set quickly gets student attention and leads into the rest of the lesson.

This isn't specific to music class - it's for all teachers! 

As an anticipatory set, teachers of some other subjects may ask students to make verbal predictions about a new story with familiar characters (ELA) or comparisons between self and the citizens of another nation (Social Studies). 

In elementary music, though, much of our focus is on procedural knowledge.

We're learning how to do something - as opposed to learning about something (declarative knowledge).