The growing interest in classroom discourse reflects a wide recognition within the mathematics education community of the critical role of social interactions in the joint construction of mathematics knowledge. An extensive body of empirical and theoretical work has been undertaken in the last two decades to characterise the types of classroom talk that are conducive to learning. Yet, a key challenge remains for mathematics teachers to orchestrate whole-class discussions so that student responses to instructional tasks can be utilised to advance the disciplinary understanding of the entire class. This is especially the case when the mathematics task in focus is both open and cognitively challenging. Drawing upon a complementary accounts methodology, we analysed the Learner's Perspective Study (LPS) classroom and interview data from two classrooms in the United States and Japan to explore teacher orchestration of student responses to rich mathematics tasks. Significantly influenced by a body of literature on classroom microculture in mathematics education, this paper employed two complementary conceptual tools, coherence and meta-discursive rules, to develop an analytical framework for the purpose of exploring epistemic coherence of classroom discourse across diverse settings. The findings demonstrated that both teachers' orchestration of whole-class discussion supported the macro-structuring of students' experience at the level of topic coherence and contextual, organisational and conceptual connectedness, whilst the meta-narratives allowed the teacher to connect their goals for mathematics teaching and learning with the ongoing classroom activities and interactions.