A density matrix description of magnetic resonance is constructed, with detailed application to spinJ = 1(or greater) particles. Different types of “monitoring” or “measurement” operators employed in atomic beam, induction, and optical experiments are constructed, and used as a compact introductory basis for the description of resonance line shapes and other characteristics of these experiments. Of particular interest are the similarities and unique differences between the optical experiments known by the names “optical pumping,” “double resonance,” and “light beats” on the one hand, and magnetic induction and atomic beam experiments on the other.