Attorneys, judges, and jurors litigating and adjudicating music copyright disputes find themselves at the intersection of two complex fields, U.S. copyright law and music theory. While most generalist judges—and the attorneys representing clients in such cases—have at least some experience with the former, very few have formal training or informal experience with the latter. As a result, legal opinions purporting to incorporate musical concepts sometimes fail to do so accurately, resulting in decisions that are inconsistent with copyright law and policy. This Article is the first in a planned series of interdisciplinary articles designed to harmonize U.S. copyright law with relevant theoretical materials from the field of music. It begins with an accessible primer on basic principles of music theory, with a special focus on the concepts of melody and rhythm. It then summarizes music copyright jurisprudence, and identifies ways in which the latter correctly and incorrectly incorporates principles of music theory. This Article demonstrates that U.S. music copyright jurisprudence is plagued with a fundamental misunderstanding of the basic musical concepts of melody and rhythm as those terms are understood within the field of music. In general, legal precedents equate melody with pitch sequence and rhythm with meter and time signature, and give primacy in their analysis to melody—as they define it—to the exclusion of rhythm. Yet as this article demonstrates, not only do music theorists define melody as consisting of pitch and rhythm combined, but their findings also demonstrate that rhythmic design plays a greater role in creating distinct melodies than pitch standing alone. The result is a jurisprudence that is both over- and under-inclusive in finding instances of copyright protection and infringement. Using both historical and contemporary musical examples, this Article concludes that courts should re-define and re-weight these two musical concepts in order to arrive at just results in music copyright disputes that are consistent with the balancing of policies that form the foundation of U.S. copyright law.