We describe the evaluation of a personal digital library environment designed to help musicians capture, enrich and store their ideas using a spatial hypermedia paradigm. The target user group is musicians who primarily use audio and text for composition and arrangement, rather than with formal music notation. Using the principle of user-centered design, the software implementation was guided by a diary study involving nine musicians which suggested five requirements for the software to support: capturing, overdubbing, developing, storing, and organizing. Moreover, the underlying spatial data-model was exploited to give raw audio compositions a hierarchical structure, and - to aid musicians in retrieving previous ideas - a search facility is available to support both query by humming and text-based queries. A user evaluation of the completed design with eleven subjects indicated that musicians, in general, would find the hypermedia environment useful for capturing and managing their moments of musical creativity and exploration. More specifically they would make use of the query by humming facility and the hierarchical track organization, but not the overdubbing facility as implemented.