The aim of our study was determine how students regulate their learning in music theory (MT). The research is based on the socio-cognitive theory of learning. The aim of our study was twofold: first, to design the instruments for measuring (meta)cognitive and affective-motivational processes in learning MT, and, second, to examine the relationship between these processes. A total of 457 fifth- and sixth- grade students from 10 different elementary music schools in Slovenia participated in the study. A questionnaire consisting of 34 items was designed to measure the student's (meta) cognitive processes and a 47-item questionnaire to measure students' affective-motivational processes of self-regulated learning in MT. Analysis showed that a lot of statistically significant correlations between (meta)cognitive and affective-motivational factors exist. The implications for educational practice, as well as future research, were also discussed. (Contains 1 table.)