While music education researchers have examined cooperating teacher and student teacher interactions via classroom observations and interviews, there is little research on extended dialogues between the cooperating teacher and student teacher or various mentoring roles (coach, guide, model, and evaluator) assumed by cooperating teachers. During one 8-week student teaching placement period, I recorded extended dialogues between four student teacher-cooperating teacher pairs, along with individual interviews. Data were analyzed using the mentor roles in dialogues model. The mentoring role assumed during dialogues reflected the student teaching context, perceptions about appropriate roles, cooperating teacher and student teacher personalities, and their relationship. Mentoring dialogues were especially influenced by unique features of the music ensemble class.