About This Issue

This issue's first article investigates the current state of the common Web browser as an environment for deploying computer music applications. The authors argue that the breadth of the tools now available from Web developers, combined with the convenience of simply accessing a URL to run a program, could have a significant impact on computer music software. The article briefly reviews past developments in this area before explaining the potential of several new standards from the World Wide Web Consortium, particularly the Web Audio API. Issues of sound synthesis, timing, input/output, and communication are considered.

The next article expands upon performance technologies that Jason Freeman and colleagues presented in the Fall 2008 and Summer 2011 issues of Computer Music Journal. Those two earlier articles concerned (1) generating music in real time and representing it in some form for performers to sight-read live on stage; and (2) improvisation by a laptop ensemble in which the performers generate and share material on the fly, using an easy-to-learn textual language for specifying sound-file manipulations. The research reported in the current article has combined and extended those efforts: The laptop performers now improvise together to generate traditional Western music notation that is read by acoustic musicians who share the stage.

The issue continues with a pair of articles on the topic listed on the spine and front cover of this issue: the automated analysis of jazz chord progressions. (This theme is reminiscent of Andrew Choi's work published in the Summer 2011 issue of Computer Music Journal, as well as work by other researchers such as François Pachet.) The first article, by W. Bas de Haas and colleagues, describes their model of functional harmonic analysis (which, though focused on jazz, also applies more generally to tonal music). Derived from an approach by Martin Rohrmeier and implemented in the functional programming language Haskell, the authors' system takes as input a sequence of symbolic chord labels and parses them to construct a hierarchical representation of the chords' relationships. The authors emphasize that their system is fast and robust against noisy data. It is also flexible, in that its rules for harmonic analysis can be modified by a user who is willing to tweak Haskell code.

The second article on this topic, by Robert Keller et al., incorporates knowledge of characteristic jazz structures such as turnarounds, dropbacks, and so on. The authors' open-source software is based on Conrad Cork's "Lego Bricks" approach to jazz analysis. A "brick" is Cork's term for an idiomatic jazz chord sequence, whose length is variable but usually constitutes one to eight measures. Cork catalogued bricks, coining mnemonic names for many, and he also categorized transitions between them. One of the co-authors has extended and modified Cork's list of bricks. The authors' system parses jazz tunes into sequences of possibly hierarchical bricks and then determines the musical key (tonic and mode) of each brick. The parsing algorithm and post-processing are shown in some detail, including the ascertainment of a minimum-cost parsing.

The final article proposes a technique for automatic identification of musical instruments in sound recordings. The authors classified thousands of monophonic musical instrument sounds using several different Bayesian network structures and a feature set consisting of peak spectral amplitudes in ten frequency windows, measured ten times per second. The authors found that Bayesian networks offer improved accuracy compared to previous methods.

The reviews in this issue appraise CDs by composers Felipe Otondo and Alexander Berne, as well as books on musical audio content analysis and on the use of software synthesizers and samplers for sound design, composition, and arranging. The always-present Products of Interest section follows the reviews. The issue closes with program notes for the included annual DVD. Curator Butch Rovan has selected eight compositions and performances involving interactive video. As is typical, the DVD also contains sound and video examples for recent CMJ articles, as well as a DVD-ROM section containing related software and data files.

Front cover. Two different analytical representations of a jazz tune's chord progression, one by Robert Keller et al. (top) and the other by W...