This paper presents an investigation into musicians' ability to control sound synthesiser parameters using various inter- faces. The principal aim was to compare separate, 1D parameter controls (touchscreen sliders) to multidimensional con- trollers (an XY touchpad for 2D, the Leap Motion for 3D). Subjects had to match a target sound as quickly and accurately as possible. Results show that after about two hours of practice, the XY pad is 9% faster than two sliders for no accuracy loss, and the Leap is 17% faster than 3 sliders with 9% accuracy loss. The multidimensional controllers improved most with practice. A new perspective on Fitts' index of difficulty is presented: "Index of Search Space Reduction" (ISSR). ISSR and retrospective accuracy thresholds on the search trajectory are used to obtain straight line plots and throughput values. These plots reveal that the Leap's speed improvement was mainly due to reaction time, but the XY pad traversed the space faster.