On Mapping EEG Information into Music - Guide to Brain-Computer Music Interfacing - page 233

relax their minds without focusing on anything in particular, and in a third to count.
Trials were carried out in a number of orders for greater disparity, and a mental
counting exercise was factored in as a test of whether musical concentration
through active and passive listening was extrinsic to standard methods of mental
concentration focusing (Miranda et al. 2003 ).
The second experiment set to determine whether EEG could identify if a subject
was engaged in musical focusing (paying particular attention to an element of music
being heard) or holistic listening (listening to music without any effort). During the
musical focusing experiments, subjects were asked to focus attention to an instru-
ment within the music that was positioned either in the left or right stereo

eld.
These tests suggested that it might be possible to accurately measure EEG
differentiation between someone engaged in mentally focusing on music and
holistic listening. The second test suggested that it might be possible, although to a
lesser degree, to record whether a subject is focusing on sound arriving in the left
ear or the right ear, whilst in both experiments, the counting exercise provided a
different response in the EEG indicating that musical focus uses different brain
processing mechanisms that other forms of concentration.
The experiments were conducted in blocks of multiple trials, and the results were
derived of ine. However, their outcomes led to two initial concepts for BCMIs. b -

soloist is a BCMI system designed to detect active and passive listening. A con-
tinuous rhythm is presented to a subject with regular melodic phrases overlaid.
Straight after the melody is played the system looks for either an EEG reading of
active or passive listening. If the reading shows active listening has occurred, then
the next melody line will be a variation of the last. If the reading shows passive
listening occurred, then the next melody played will be exactly the same as the last
(see also Chap. 1 ) . b - conductor was designed to use musical focusing to affect
changes in either left or right channels of music (Fig. 10.4 ). When presented with
music in both channels, a user selects a channel through attentively focusing on the
instrumentation it contains. At regular intervals, the system detects the channel of
attention in the EEG, and this recognition is mapped to the music, turning up the
volume of the focused channel. After a change is made, the volume then returns to a
default value until the next command to change is received.
In 2004, Miranda and colleagues reported on a further experiment that investi-
gates EEG derived from auditory imagery. In this, they further the search for
distinctions between mental tasks looking for any distinguishable differences
between active listening and tasks based on motor imagery and spatial navigation ,
whereby a subject focus their attention to a physical movement whilst remaining
still (Miranda et al. 2004 ). Tests again used power spectrum analysis but with three
pairs of electrodes (7 in total with a reference electrode) to determine a classi

cation
system through building a neural network. The three extra tasks assigned were for a
subject to imagine opening and closing the right or left hand (motor) and to imagine
scanning the rooms of their home (spatial). A separate pair of electrodes read EEG
data corresponding to each task, and the voltage difference between the pairs was
derived. It was observed which pair produced EEG readings that could be most