Music education is supported by an increasing range of digital technologies that afford a remarkable divergence of opportunities for learning within the classroom. Musical creativities are not, however, limited to classroom situations; all musicians are engaged in work that traverses multiple social and physical settings. Guided by sociocultural theory of human action, this paper presents a case-study analysis of two computer-based composers creating one soundtrack together. Analysing how collaborative work was undertaken in all of the naturally occurring settings, this paper shows how the students' interrelationships with technology constituted their understandings, creative output and their ecology of practice. The research contributes new knowledge about how digitally resourced creating is shaped by remote, remembered, hypothetical and imagined digital technologies. It also shows how technology-mediated co-creating is a complex interactional accomplishment, implicating the value of long-term multisetting digital co-creating to higher mental development through discourse within music education.