In the Romantic period, expanded tonality offers a creative challenge to composers as they explore new ways of establishing the hierarchy of pitches and utilizing the chromatic and diatonic resources. Prominent compositional techniques of this period include the use of linear harmony with less clearly defined root movements, the structural placement of dominant function, new approaches that redefine tonal stability, motivic treatment that generates harmony and form, flexible treatment of rhythm and meter, and functional treatment of chromatic pitches. This study explores the ways in which characteristics of the Romantic period are influenced by the upper/lower leading tone and the effects of compositional treatment on the expansion of tonality. In addition, this study includes two supportive concepts: (1) the wedge and toggle switch by David Witten and (2) The Neapolitan Complex by Christopher Wintle. In describing techniques in expanded tonality, excerpts from compositions by Robert Schumann and Johannes Brahms (both prominent composers of the Romantic period) are used to establish the significance of these techniques. In the fourth movement of Sonata in E minor "Undine," by Carl Reinecke, the structural treatment of the upper/lower leading tones to tonic and dominant are very prominent features that contribute significantly to the development of the concepts in this study.