Chord-Sequence-Factory: A Chord Arrangement System Modifying Factorized Chord Sequence Probabilities

This paper presents a system named ChordSequenceFactory for automatically generating chord arrangements. A key element of musical composition is the arrangement of chord sequences because good chord arrangements have the potential to enrich the listening experience and create a pleasant feeling of surprise by borrowing elements from different musical styles in unexpected ways. While chord sequences have conventionally been modeled by using Ngrams, generative grammars, or music theoretic rules, our system decomposes a matrix consisting of chord transition probabilities by using nonnegative matrix factorization. This enables us to not only generate chord sequences from scratch but also transfer characteristic transition patterns from one chord sequence to another. ChordSequenceFactory can assist users to edit chord sequences by modifying factorized chord transition probabilities and then automatically re-arranging them. By leveraging knowledge from chord sequences of over 2000 songs, our system can help users generate a wide range of musically interesting and entertaining chord arrangements.