Music search by nature does not allow users to grasp items of interest at a glance unlike image search. Fast and efficient music search is particularly important for active listeners or content creators in the media industry who use music as part of the media production. To this end, we propose a type of visual music thumbnail, Content-based Visual Music Thumbnailing, that allows users to search and browse music tracks with visual cues, and conduct a user study to verify the proposed concept. We first present the focus group interviews to draw out important musical attributes for music search and then map the attributes to graphic components to generate the thumbnail image of a music track. We validate the proposed visual music thumbnail on a web-based survey system that compares the thumbnail-based interface to the conventional text-based interface. The system measures the number of clicks, rank score, and completion time while the participants are conducting given music search tasks. The results show that the visual music thumbnail-based interface outperforms the conventional text-based interface in the measured metrics.