The Use of Recursive Median Filters for Establishing the Tonal Context in Music

The recursive median filter is used to improve the structure of the output of the key finding algorithm for establishing tonal contexts of musical patterns in a musical composition. This is subsequently incorporated into a system for recognition of musical patterns. Krumhansl’s key-finding algorithm is used as a basis. The sequence of maximum correlations that it outputs is smoothed with a cubic spline and is used to determine weights for perceptual and absolute pitch errors. Maximum correlations are used to create the assigned key sequence, which is processed by a recursive median filter. In most cases, the recursive median filter establishes the key more accurately than the standard median filter. Additionally, since the recursive median is idempotent, the key-finding output is guaranteed to be a root signal.