A PROGRAMED TEXTBOOK IN MUSIC THEORY WAS DEVELOPED FOR A MUSIC COURSE REQUIRED OF STUDENTS PREPARING TO BE ELEMENTARY TEACHERS. FIVE DIFFERENT GROUPS OF STUDENTS, OVER A PERIOD OF FIVE SEMESTERS, WERE GIVEN VARYING KINDS OF INSTRUCTION TO EVALUATE MATERIALS FOR THE TEXTBOOKS. GROUP 1 RECEIVED FACE-TO-FACE INSTRUCTION IN MUSIC THEORY BUT NO PROGRAMED INSTRUCTION. GROUP 2 USED A TENTATIVE PROGRAM AND PARTICIPATED IN REVISING AND REARRANGING IT. GROUP 3 USED THE PROGRAM AND RECEIVED NO FACE-TO-FACE INSTRUCTION. GROUP 4 PARTICIPATED IN FURTHER REVISION OF THE MATERIAL. GROUP 5 USED THE FINAL VERSION OF THE PROGRAM AND RECEIVED NO FACE-TO-FACE INSTRUCTION. ANALYSIS INDICATED THAT GROUP 2 ACHIEVED MORE THAN ANY OF THE OTHER GROUPS. CONTINUAL OBSERVING, REVISING, AND TESTING APPEARED TO RESULT IN EFFICIENCY AND ENJOYMENT FOR THE TEACHER TRAINEES. GROUP 5 LEARNED AS MUCH MUSIC THEORY AS GROUP 1 AND ACCOMPLISHED THEIR LEARNING IN LESS TIME. (GD)