Start with compact, high-yield reading. Music: A Very Short Introduction is useful for thinking critically about music across culture, performance, history and listening, while A History of Western Music gives a broad historical framework.
For a wider intellectual range, Musicking: The Meanings of Performing and Listening pushes you to treat music as social action, The Rest Is Noise: Listening to the Twentieth Century opens twentieth-century listening through politics and culture, and The Study of Ethnomusicology: Thirty-Three Discussions introduces ethnomusicological questions.
Use video to sharpen explanation, not to replace reading. Adam Neely can help you turn theory, jazz, notation and listening into spoken argument, which is useful for interview discussion. 12tone is useful for practising concise harmonic and formal analysis. Early Music Sources connects historical evidence to performance practice, helping you discuss how sources shape interpretation. David Bruce Composer is useful for composition-minded applicants because it models how to explain orchestration, rhythm, harmony and creative decisions.
For regular listening and argument-building, The Listening Service, Music Matters, Sticky Notes: The Classical Music Podcast and Song Exploder all give different models for turning sound into explanation.
Structured courses can fill gaps. Fundamentals of Music Theory, Listening to Music, Fundamentals of Music and Computational Music Theory and Analysis cover theory, listening, notation and analytical approaches.