This paper describes the design and development of The Un-finder, a prototypical interface that allows users to searchand improvise music with audio files from a large localrepository using music information retrieval based on con-tent and metadata. The research is part of an ongoingproject (IRESAP) concerned with tools incorporating cur-rent music information retrieval strategies that both sup-port artistic practices and have utility outside of a perfor-mance setting. In The Unfinder, we aim to exploit the bal-ance between accurately and reliably retrieving audio ma-terial from a file search system, and the potential for failurein the system to do so. Our prior research is used to framedesign choices which are measured with a user study usedto evaluate the interface. In the study we observed nineusers of varying musical backgrounds playing with the in-strument while taking notes of their utterances and ideas.The transcriptions of the user’s comments were analyzedusing a thematic analysis method and five (5) themes wereidentified: perception, parameterization, identity, agency,and imaginaries. These themes indicate that the interfacedesign is promising for artistic output, the use of a singlefeature for searching does not have much perceptual rel-evance, and the chosen features are useful for discoveringaudio files within serendipitous musical situations.