Empirical Classification for Musical Information Retrieval

In the continuing goal of codifying the classification of musical sounds and rules for data mining we present the following classification methodology that produces a hierarchical granulation structure. The motivation for this paper is based upon the fallibility of Hornbostel/Sachs, the generic classification scheme used in Music Information Retrieval for instruments. In eliminating the redundancy and discrepancies of Hornbostel/Sachs’ classification of musical sounds we present a procedure that reduces the musical attributes empirically and defines a robust rule discovery. Rather than using classification rules based directly on Hornbostel/Sachs, we rely on the empirical data of the log attack, sustainability and harmonicity. We propose a classification system based upon the empirical musical parameters and then incorporating the resultant hierarchical granulation structure for classification rules. 1 Instrument Classification Information retrieval of musical instruments and their corresponding sounds has invoked a need to constructive cataloguing conventions with specialized vocabularies and other encoding schemes. For example the Library of Congress subject headings [1] and the German Schlagwortnormdatei Decimal Classification both use the Dewey classification system [2, 3] In 1914 Hornbostel-Sachs devised a classification system, based on the Dewey decimal classification which essentially classified all instruments into strings, wind and percussion. Later it went further and broke instruments into four categories: 1.1 Idiophones, where sound is produced by vibration of the body of the instrument and 2.2 Membranophones, where sound produced by the vibration of a membrane. 3.3 Chordophones, where sound is produced by the vibration of strings and 4.4 Aerophones, where sound is produced by vibrating air. For purposes of music information retrieval, the Hornbostel-Sachs cataloguing convention is problematic, since it contains numerous exceptions and follows a subjective humanistic conventions making it incompatible for a knowledge discovery discourse. For example, a piano emits sound when the hammer strikes strings. The striking of an object is percussive yet its the string that emits the sound vibrations which also classifies it possibly as a chordophone. Similarly, the tamborine comprises a membrane and bells making it both an membranophone