This is the first curricular lesson of the year in my secondary music theory class. I have students take written notes as I go through all of this on the board. This lesson usually takes us 2-3 classes initially, and we continue to review it until all students have a basic understanding (as well as the material in their binders).
This unit introduces clefs, the musical alphabet, and the basic concepts of pitch. Look to Unit Two for rhythm and time signatures!