Information Technology Reference
In-Depth Information
nes the
constraints put upon a valid continuation of the music. These constraints will limit
the available options one by one and will order them according to the de
In the given phrase structure, the rule that follows from BAR then de
ned rule
preferences. The CLOSE constraint will order the available options according to
their closeness to the stored value. For example, after choosing:
(SCHU-1-1-MEA-1
P-CLASS ((0 4) (0 3 4 6 7 9))
P76
PCL ((2 7 11)(2 5 7 9 11))
PL 83
BAR INC
CO SCHU)
as the beginning, PREV-PITCH-LEADING will have stored 83, and PREV-
PITCH-CLASS-LEADING will have stored ((2 7 11) (2 5 7 9 11)). This will result
in measure 2 and 4 being ranked highest according to both pitch and pitch-class,
while measure 6 is also quite close according to pitch. This weighted choice will
give a degree of freedom in the decision that is needed to generate pieces with an
element of surprise. The music will not get stuck in repetitive loops, but it will
nd
the closest possible continuation when no perfect match is available. We can still
find a close match in this way if the third constraint eliminates all the obvious
choices that are available, e.g. because a jump is requested to the musical elements
of another composer, who might not use the same pitch-classes and pitches.
Figure
1.3
shows an example of resulting music with elements from the musical
style of Schumann and Beethoven. In this example, the EEG jumped back and
forth, from bar to bar, between the two styles. The harmonic and melodic distances
are quite large from bar to bar, but they are the optimal choices in the set of chosen
elements from the two composers.
After a few training sections, colleagues in the laboratory were able to increase
and decrease the power of their alpha rhythms in relation to the beta rhythms
practically at will, therefore being able to voluntarily switch between two styles of
music. We noticed that the signal complexity measurement tended to be higher
when beta rhythms were more prominent in the signal: the music in the style of
Beethoven tended to be played slightly louder and faster than pieces in the style of
Schumann.
At this point, I went on to address my second dreamed scenario: Would it be
possible to build a BCMI system for a person with locked-in syndrome to make
music?
As it turned out, after a critical evaluation of our system, informed by opinions
and advice from health professionals and music therapists working with disable
patients, I concluded that the BCMI-Piano was neither robust nor portable enough
to be taken from the laboratory into the real world. The system comprised two
laptops, two bulky hardware units for EEG ampli
cation and too many dangling
cables. Moreover, the skills required for placing the electrodes on the scalp and run
