Classification of melodies by composer with hidden Markov models

The authors use hidden Markov models (HMMs) for abstracting the style of a composer and for recognizing it from an unknown excerpt. We employed a data set of 605 musical themes written by five well-known composers (Mozart, Beethoven, Dvorak, Stravinsky, Beatles). A preliminary investigation based on descriptive statistics served the purpose of choosing a group of suitable music representations. Then, for each representation and for each composer a HMM was trained with the subset of melodic lines extracted from the pieces. An unknown melody is then classified as belonging to a composer if the corresponding HMM gives the highest probability for that sequence. Experiments with Markov chains and tests on human subjects were used as a term of comparison. The best results achieved with HMMs was 42% successful classifications on average, obtained with an alphabet of intervals between -10 and +10 semitones and with HMMs of order 18. In the case of human classification based only on stylistic assumption, we measured 24.6% for music amateurs and 48% for music experts. In conclusion, HMMs performed nearly as well as a music expert in the classification of melodies by composer, nevertheless, memory models have been proven to play a fundamental role in the process of music classification and need to be taken into consideration for practical applications.