“Anything made by man, no matter how many varieties it assumes, and how much of the superhuman it seems to contain, must reveal its secret to the close observer.” Paul Hindemith (1942: 176). “Are you one of those guys who wants to put crutches under my ass?” Lonnie Johnson (Keil 1966: 35). It is the aim of this thesis to define a musical genre by showing how, in the realisation of an improvisation, two key elements – the physical layout of a musical instrument and human movement patterns – are combined to produce music. This thesis takes as a model the twelve bar blues form, and examines the above aspects in the output of two pioneering figures of the melodic improvised guitar: Lonnie Johnson and T-Bone Walker. The thesis is in divided in to three sections; the first, which considers context, is divided in to four topics. • Identification of the model – the twelve bar blues form, and an examination of the meaning of the model to black culture. • Consideration of the role of geography on the emergent style • The guitar design and development. • Identification of the pioneering figures of the genre. The second section, which is concerned with musical, physical and analytical aspects, surveys theories of scale, mode, blues scale and blue notes, and suggests that blues improvisation is inextricably linked to spatio-motor based patterning. A geographical layout of the guitar is presented to aid in the analytical process. The third section is analytical and attempts to identify the melodic ‘characteristics of the blues guitar genre. A series of transcriptions were made of improvisations of early blues guitar soloists. These are analysed by reduction and expansion. The tones produced in the improvisations were reduced to a modal hierarchy of principal, secondary and incidental tones which are presented on a fretboard form of notation. The resulting mode is reduced to a scale which is compared to theoretical definitions of blues scale. This raw data is then expanded by considering the left hand gestural movement between tones. gestures are seen to be linked together to form cells. These are sub-grouped in to various types. Larger structures, motives, are then defined as comprising several cells. The location of the cells in the model is indicated. These are categorised in groups for each performer. Thus improvisation is presented as an interaction, which takes place in time and space, between left hand movement strategies of the performer and the surface of a musical instrument.