This thesis examines the improvisations of jazz pianist Paul Bley, asking the questions: In Paul Bley's improvisations, what constitutes the melodic vocabulary, in what ways is that vocabulary organized, and to what extent does it reflect the 'jazz language'? Further, in what ways does Bley create coherence and continuity in his solos? To propose answers to these problems, a selection of Bley's improvised solos were transcribed and examined using techniques described in the methodology section. These techniques attempt to consider both the process and the product of the activity of improvisation. This research revealed that Bley's approach utilised several techniques pioneered by jazz saxophonist Ornette Coleman as well as melodic, harmonic and rhythmic devices common in the jazz idiom. Continuity and coherence were found in the sample, and this was largely attributable to the ways Bley created thematic unity by using recognisable motifs repeatedly in a variety of (often contrasting) contexts. In addition to the transcriptions, these findings are supported by extracts from interviews with Paul Bley conducted by the author and included in the appendices.