This study investigates the historical and musical background that led the Panamanian composer Natanael Mojica to create the work "Fantasía 'De la Noche' op. 33" for trombone and piano. The interpretative and stylistic context is analyzed, as well as the musical resources employed, contributing to the Latin American compositional literature. A qualitative approach was adopted, using semi-structured interviews with Mojica, a comprehensive literature review on the history of the trombone and Panamanian music, and a musical analysis of the work. The interviews provided information about the composer's influences and creative process. The findings reveal that the work combines elements of classical sonata form with modern harmonies, reflecting the duality of the night. Distinctive rhythmic and harmonic patterns were identified that enrich the repertoire of the trombone as a solo instrument. The "Fantasía 'De la Noche'" represents a significant contribution to the Panamanian trombone repertoire, highlighting Mojica's compositional innovation and opening the door to future research on the evolution of contemporary Latin American music.