The way rhythm is taught in Western classrooms and music lessons is rooted in a centuries-old European approach that favors metric levels within a grand symmetrical grid. Swinglines encourages readers to experience rhythms, even gridded ones, as freewheeling affairs irrespective of the metric hierarchy. At its core, this book is a nuts-and-bolts study of durational comparisons in the context of creative expression. It shows that rhythms traditionally framed as "deviations" and "non-isochronous" have their own identities. They are coherent products of precise musical thought and action. Rather than situating them in the neither-here-nor-there, author Fernando Benadon takes a more inclusive view, one where isochrony and metric grids are shown as particular cases within the universe of musical time. Rhythms that do not readily comply with the metered regime are often regarded as anomalies and deformations. The music explored in this book demonstrates how readily this paradigm vanishes once the frame is flipped from what rhythm is not to what rhythm is. As conceptualized here, swing flattens the temporal field to consider how note values relate to one another by any magnitude, not just the simple ratios of traditional theory. Musical analyses illustrate the book's concepts with the aid of transcriptions and timing-data visualizations. Variation, tuplets, polymeter, displacement, phrase structure, rhythmic counterpoint, parallel tempos, cyclical patterns, and time signatures are shown to be particular expressions that draw their contours from the swing continuum. They showcase the rich diversity of rhythm and propose ways to reframe how we think about musical time.