Our research group is currently working on the user interface and interaction redesign of CODES, a system for collective music creation on the Web. Cooperative work over a piece of music in CODES follows a cyclic, prototyping approach, which brings some challenges for interaction design. This poster summarizes our redesign concept guidelines, the problems we identified through evaluation of the previous version, and our proposed solutions. The main issues addressed were task conformance, site structure and navigation, aesthetics, and simplicity.