Craig Sapp's KeyScapes are visualizations of harmonic structure. Sapp began to develop them as a graduate student at the Center for Computer Research in Music and Acoustics at Stanford University in the late 1990s. Although keyscapes are useful in giving a synoptic view of the harmonic structure of single movements and/or works, their use in the aggregate indicates many changes over time.
The initial Tonal Landscape Gallery gives a brief visual introduction. Here, for example, is a table of keyscapes representing each movement of the 32 Beethoven piano sonatas. Tonal architectures between movements of single works and changes in this relationship are particularly visible.
For large-scale comparison functional (relative) harmony (divorced from a specific key) proves more useful than exact-pitch (absolute) mapping, as this representation of the same Beethoven sonatas shows.
Every piece at Sapp's KernScores website provides a virtual keyscape that may be absolute or relative. In movements with repeats, the user may select a view with or without repeats included. Sapp's doctoral thesis (2011) show extensive comparisons. In other writings he has used the same technique to discover biases in multiple approaches to harmonic analysis used today.
Music Animation Machine
Stephen Malinowski's Music Animation Machine (MAM) is well-known in computer-music circles but is underutilized in classrooms, where its value transcends diverse levels of education and musical training. Originating in California in 1985 and continuously improved ever since, it works like a video-camera for the inner workings of music fabric. It presents a wide range of geometrical objects moving across the viewer's screen. Depend on its settings it can emphasize relationships between pitches, harmonies, rhythmic values, loudness, and so forth. Viewers will find rhythmic patterns and contrapuntal refinements of the music being viewed hard to miss. Although MAM was originally dependent on MIDI, it has been retooled to work in live concert settings. Malinowski's Youtube channel (smalin) offers the best current (graphical) lexicon of its offerings, but other MAM websites include the history of its gestation and development, freeware (Windows only), sample files (ibid), and miscellaneous items.
An ongoing catalog of animated graphical scores is available at Music Worth Watching. Over time the methods of varieties of visualization have increased to better accommodate the wide array of moods that will be "seen" from piece to piece.
Ptolemaic: Musical Visualization and Analysis
This set of software tools displays dynamic renderings of music in relation to several concepts from music-theory: pitch class, tonal pitch-space, and functional harmonic analysis. Tools are freely downloadable.
Craig Sapps TimeScapes facilitate rapid comparison of differences in timing in recorded performances. They have played a major role in his work with the CHARM Mazurka Project directed by Nicholas Cook (2005-07). Companion software tools are available through the Sonic Visualizer website. The TimeScapes concept is derived from Sapp's earlier work on KeyScapes (see above).