Extant communication theories predate the explosion of digital formats and technological advances such as virtual reality, which likely explains their predominant focus on traditional and format-level (e.g., face-to-face, email) rather than digital or characteristic-level (e.g., visual cues, synchronicity) design decisions. Firms thus lack insights into how to create and use emerging digital formats, individually or synergistically. To establish a holistic framework of bilateral multiformat communication for relationship marketing, this article reviews communication theory to establish a foundation for understanding multiformat communication and to identify any gaps (e.g., AI agents, simulated cues). The authors then review bilateral communication research in light of the identified theoretical gaps, to inform their framework. Finally, by decomposing these formats according to six fundamental characteristics, they predict how each characteristic might promote effective, efficient, and experiential communication goals, in light of distinct message, temporal, and dyadic factors. Ultimately, these combined insights reveal an overarching framework, with characteristic-level propositions grouped into five key themes, that can serve as a platform for academics and managers to develop multiformat communication theory and relationship strategies.

Current research often relies on narrowly focused experimental methods that address just a few independent variables or correlational designs, despite calls for future research to take big-picture perspectives that offer real-world applicability and causal evidence. This disparity likely reflects the constraints imposed by the need for extensive resources to conduct broad, causal examinations. To bridge this gap, the current article presents the Taguchi approach to large-scale experimental design, which remains notably underutilized in marketing research despite being well-established in other fields. Its effectiveness stems from the robust catalog of experimental design rubrics that can incorporate many different independent variables systematically and efficiently. The causal and efficient experimental option for broad scopes of investigation embraces the embeddedness of independent variables and thus can help build marketing theory and advance practice. This article details the fundamentals of the Taguchi approach, its relative advantages, and a three-step implementation process.