Sixteen types’ chord label estimation from acoustic signal of electric guitar

Abstract

It’s difficult to determine an chord label for acoustical signal of musical playing, in particular when playing chords with “omitting”, “inversions,” or “tension voicing” on the guitar. Additionally, “enharmonic equivalence” produces multiple possibilities. This study developed a chord estimation system that deals with an audio signal output from electric guitars considering such techniques. All of the chord types employed in this study are the sixteen patterns frequently used in guitar chord playing. Chord labels are estimated by combination of salient pitch classes (or chroma), and some of them are dealt with as “performed notes” assumed as the member of played chord. Obtained performed notes are input to the “search tree for chord labels” so as to search possible chord labels, by referring chord progression patterns included in the “chord progression database.” Sixteen chord types are triad such as major, minor, aug, dim and sus4, with four-note chords such as 6th, 7th, Maj7, aug7, 7sus4, add9, min6, min7, minMaj7, min7(b5), and dim7. This study investigated appropriate threshold and type of filter used in the judgment of performed note. Results found that chord labels are estimated as 89% of accuracy when using three types of electric guitars.