About Spectral Mappings

Spectral mapping is a technique for moving the overtones of a sound to any desired location. For example, the figure below shows a harmonic sound (in blue) that is transformed into an inharmonic sound (in green). In this case, some of the overtones are increased in frequency and some are decreased (as indicated by the orange arrows).



Spectral mappings lie at the heart of the TransFormSynth because they allow precise control over the spectral aspects of timbre. You can read the original paper describing spectral mappings (which appeared in the Computer Music Journal in the Spring issue of 1998).

The timbre slider (in the "linear keyboards" and "scala tuning tables" windows) and the tonality diamond (in the 2-dimensional tuning continua windows) control how much tempering is applied to the timbre: at one extreme the overtones are mapped to a harmonic template. At the other extreme they are mapped so as to best "line up" with the given tuning.