PhDIn this thesis we address the subject of automatic extraction of harmony
information from audio recordings. We focus on chord symbol recognition
and methods for evaluating algorithms designed to perform that task.
We present a novel six-dimensional model for equal tempered pitch
space based on concepts from neo-Riemannian music theory. This model
is employed as the basis of a harmonic change detection function which
we use to improve the performance of a chord recognition algorithm.
We develop a machine readable text syntax for chord symbols and
present a hand labelled chord transcription collection of 180 Beatles songs
annotated using this syntax. This collection has been made publicly available
and is already widely used for evaluation purposes in the research
community. We also introduce methods for comparing chord symbols
which we subsequently use for analysing the statistics of the transcription
collection. To ensure that researchers are able to use our transcriptions
with confidence, we demonstrate a novel alignment algorithm based on
simple audio fingerprints that allows local copies of the Beatles audio files
to be accurately aligned to our transcriptions automatically.
Evaluation methods for chord symbol recall and segmentation measures
are discussed in detail and we use our chord comparison techniques
as the basis for a novel dictionary-based chord symbol recall calculation.
At the end of the thesis, we evaluate the performance of fifteen chord
recognition algorithms (three of our own and twelve entrants to the 2009
MIREX chord detection evaluation) on the Beatles collection. Results
are presented for several different evaluation measures using a range of
evaluation parameters. The algorithms are compared with each other in
terms of performance but we also pay special attention to analysing and
discussing the benefits and drawbacks of the different evaluation methods
that are used