If similarity takes place between different fragments from one musical piece, a musical similarity implies a repetition of the first occurring fragment.
As well, eventually, the similarity does not occur by direct repetition, but by presenting in two (or more) set of relations, some common values or patterns.
Objective musical similarity can be based on musical features such as: Pitched parameters Non-pitched parameters Semiotic parameters Nevertheless, similarity can be based also on less objective features such as musical genre, personal history, social context (e.g. music from the 1960s), and a priori knowledge.
Similarity is relevant also in music information retrieval.
[4] Automatic methods of musical similarity detection based on data mining and co-occurrence analysis has been developed in order to classify music titles for electronic music distribution.