Automatic arrangement for the bass guitar in popular music using principle component analysis

Abstract

In popular music, the drums and bass guitar create the rhythm. In 2008, we developed a drum pattern database including thousands of music excerpts to investigate the role of drums. However, no studies have been reported on using a large number of samples to investigate the role of the bass guitar in popular music. Moreover, it has been difficult to generate appropriate phrases on automatic-arrangement systems. We propose a method that we have developed for identifying the bass part using Musical Instrument Digital Interface (MIDI) excerpts. In the method, each one-bar length is identified as either a bass guitar part or not, and if it is, it is appropriately named a ``bass guitar pattern.'' The basic information of the bass guitar pattern, such as onset, interval, and dynamics profiles, was extracted from it and a database comprising these profiles was constructed in order to extract common features among patterns. We use principal component analysis (PCA) to introduce several automatic-arrangement parameters, including those in the proposed database, and call these parameters ``eigenphrases of the bass guitar.'' We propose a method of arranging the bass guitar part to generate an appropriate pattern as a musical phrase by multiplying each of the principal component vectors from the eigenphrase of the bass guitar with relative weights. The method is confirmed to be effective as a means of generating bass guitar parts in a natural rather than an artificial way.