Sixty undergraduate students who had completed at least one semester of jazz improvisation were assigned to either: (a) physical practice (PP); (b) mental practice (MP); (c) combined 66 percent PP and 33 percent MP (66%PP:33%MP); and (d) combined 33 percent PP and 66 percent MP (33%PP:66%MP) groups. Subjects were to perform a 3-1-7-5 tonal pattern over two difficulty levels of chord progressions. A pre-test, a three-minute practice session, and a post-test were performed for each progression. ANCOVA results revealed significant interaction between groups and task difficulty. Post-hoc t-test revealed superior results for both MP and 33%PP:66%MP on the easy task compared with the hard task. The four groups were collapsed into two groups: (a) PP and 66%PP:33%MP, both high in percentage of PP (HPP); and (b) MP and 33%PP:66%MP, both high in percentage of MP (HMP). Post-hoc t-test revealed a significantly superior performance of the HPP to that of the HMP on the hard task. (Contains 4 figures and 7 tables.)