A novel approach to symbol detection in optical music recognition is presented. The binarized image of a scanned score is transformed into an intermediate representation by computing its contours and assigning additional visual features to them. The resulting contour points are accessed via a high dimensional spatial index that aids a heuristic search to detect a given symbol as described by a template image. An automatic and a manual method for generating ground truth data are presented, amongst other web-based tools to evaluate and supervise the recognition process.