Jazz on the Line: Improvisation in Practice presents an ethnographic reflection on improvisation as performance, examining how musicians think and act when negotiating improvisational frameworks. This multidisciplinary discussion—guided by a focus on recordings, composition, authenticity, and venues—explores the musical choices made by performers, emphasizing how these choices can be logically understood within the context of controlled, musical outputs. Throughout the text, the author engages directly with musicians and their varied practices—from canonized dogmas to innovative experimentalism—offering interviews both planned and spontaneous. Musical agency is posited as a tightrope balancing act, signifying the skill and excitement of improvisational performativity and exemplifying the life of a jazzaerialist. With a travel journal approach as a backdrop, Jazz on the Line provides concepts and theories that demystify the creative processes of improvisation.