musical patois - interactive

The applet interface consists of a main graph area, a menu bar above the graph, a theme panel below the graph, and an evolver panel to the right of the graph.

nPVI vs. MIV graph

The large upper left panel presents a plot of NPVI vs. MIV values for a collection of themes.

The average speech nPVI x MIV values for English and French speech are marked by a red cross and a blue cross respectively. The crosses indicate standard deviations, as in Patel et al. (2006).

The collection of plotted themes can be assembled from the library of themes used in (Patel et al., 2006), through the Library menu. The library contains themes from English composers Bax, Delius, Elgar, Holst, Ireland and Vaughan-Williams, and from French composers d'Indy, Debussy, Faure, Honegger, Ibert, Milhaud, Poulenc, Ravel, Roussel and Saint Saens. The menu offers options to load all themes, all English themes, all French themes, or all themes from any of the featured composers. The collection is not reset when loading a new subset, such that any combination of these options may be plotted. (The Clear button in the Population panel empties the theme collection and therefore clears the graph.)

Each theme in the collection is represented on the graph by a small blue square at the position corresponding to its nPVI and MIV values. A click on or near a blue square selects the corresponding theme (marked as a solid red square). The theme panel displays information specific to the currently selected theme.

A large black square marks the position of the theme collection's average nPVI and MIV values in the graph.

theme panel

The upper part of the theme panel displays information about the theme currently selected. The panel shows, from left to right, the theme's name, its nPVI and MIV values, and the replay tempo in beats per second (bps). The play button triggers replay of the theme through the default MIDI player; the stop button stops the replay.

The theme name and replay tempo can be edited by the user (change the value in the appropriate field and press return). For themes loaded from the library, the default name is the original file name. The default replay tempo is 120 bps.

The lower part of the theme panel displays the notes and durations in piano roll notation. The blue line indicates A440; the graduations indicate tempo units.

In addition, to facilitate transcription, the display shows letter names (pitch spelling consistent with C Major).

The piano roll area can be scrolled horizontally by dragging with the mouse. The beat scale can be changed by holding SHIFT while clicking, then dragging vertically in the piano roll area. The total number of beats displayed in the width of the panel is indicated while rescaling.

evolver panel

The evolver panel comprises of several buttons that command the creation and evolution of theme populations, as well as some information about the current population: its age (in number of generations), and its average nPVI and MIV values.

The top buttons provide a means to clear the current population (button labeled Clear) and to seed the population with 50 randomly generated themes (button labeled Init).

The remaining buttons control the evolution of the current population into the next.

The radio buttons labeled English and French indicate which nPVI and MIV values are desired for the populations. Technically, the genetic algorithm will select themes closer to the average nPVI x MIV point for the selected language. A click on the button labeled Evaluate computes the fitness for each theme in the population and sorts the themes according to their fitness.

A click on the Select button marks the themes that are most fit as breeders. Technically, this selection mechanism is called elitism. The number of breeders is half the size of the total population. Breeders are colored green on the nPVIxMIV graph.

A click on the Breed button triggers the creation of the next generation from the set of selected breeders. Each new theme in is created by picking a parent at random among the breeders, and copying its note events with possibly some mutations that can result in changing the note pitch, the note duration, or drop the event (in which case the previous note's duration is extended) or split the note (without changing the total duration of the events). These operators were chosen for their ability to alter a theme's NPVI or MIV values, rather than for specific musical properties (this is a very difficult, unsolved problem in the general case). The newly created theme takes the name of its parent, to make it easier to track origins. Note that a theme's name can be changed in the Theme panel.

Starting from a given population, either generated randomly, or assembled from the library of themes, or evolved from a previous population, a new generation is produced by going through the cycle: Evaluate - Select - Breed.

Pressing the button labeled Evolve is equivalent to pressing in sequence Evaluate, then Select, then Breed.

Disclaimers:

The genetic operators adopted here are quite simplistic. The full arsenal of genetic algorithm and evolutionary computation methods comprise much more elaborate theoretical and practical tools, which unfortunately are very difficult to apply to music in a meaningful way.

There is no claim that this applet can generate musically meaningful themes. In fact, there is no musical knowledge (explicit or implicit) in the code. The library of themes constitutes the only musical material. For all it knows, this program could be evolving phone book entries...