Identifying precisely what teachers do to elicit desired changes in their students' knowledge and skill is a long-lasting challenge of educational research. Here, we use conversation analysis to contribute to a deeper understanding of this matter by considering how Finnish-speaking musical instrument teachers use directives to guide their students. Our data consist of 10 video-recorded instrument lessons (violin, piano, guitar, and ukulele). In our findings, we provide an account for the variance in the musical instrument teachers' use of six second-person directive forms in Finnish. We argue that the teachers' choices between these directive forms are warranted by three dimensions of the participants' conduct: (1) location of the directive within the participants' wider activity structure, (2) degree of the student's cooperation at the given moment, and (3) the institutional priority of action that is being called for.