Tuning the Ear is an ear-training book that develops listening skills through the practice of just intonation, approaching tuning as both a perceptual experience and a concrete musical system grounded in ratio-based harmonic relationships. Through guided exercises, analytical examples, and clear conceptual frameworks, the book trains readers to hear beating, resultant tones, and interval color while engaging directly with the practical realities of 7-limit just intonation—including ratio thinking, commas, and modal organization. By integrating listening, calculation, and creative application, Tuning the Ear presents just intonation as a living practice in which theory and ear inform one another, offering performers, composers, and curious listeners a practical path toward deeper musical awareness.