Vladimir Viro’s Music Ngram Viewer is one of the most interesting search tools I’ve ever seen. Enter a sequence of pitches and/or rhythms, and the application will scour the available literature via IMSLP to discover instances of your query either at pitch or in transposition—the searches are adjustable by numerous parameters. Searching for a brief melodic sequence from the overture to Mozart’s Le nozze di Figaro produced the following result, including a searchable chart (at lower left) showing the frequency distribution of the queried figure across the history of the literature:
The project is a work in progress—I was less successful at searching for characteristic rhythms, for example—but the overall functionality and the diversity of features offered are impressive. Too cool.