The purpose of this study was to explore the phenomenon of musical improvisation within two contrasting musical genres — jazz piano and liturgical and concert organ. While improvisation is well documented in both genres, there is little literature relating the two forms and, in particular, the process of improvisation. The aim of this study is to contribute to this dialogue. In encounters with two experienced improvisers, several key areas are identified. In particular, improvisation in both forms draws heavily on pre-existing and pre-rehearsed material both as a starting point and as exemplar material, and so therefore exposure to and immersion in both forms is necessary for successful mastery. Improvisation in both traditions is far from instantaneously conceived music (that is — made up entirely from scratch); indeed, it exists within a tight socio-musical framework. Deviation from this framework can lead to confusion for both performer and audience. Improvisation is affected not only by the intentions of the performer, but also by the expectations of the audience. Musically, improvisation cannot be said to be fully autonomous. Meaningful improvisation, then, should take place in an appropriate context.