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conditions, respectively. As a result of the contiguity of groups, the
first stimulus in
each group followed the atonal stimulus in the previous group (except for the initial
group), which was de
ned as the
initial
condition. The
distant
and
close
conditions
therefore de
ned changes from one key to another (distant or close, respectively),
whereas the
same
condition de
ned no change of key (i.e. the next stimulus was in
the same key). The
atonal
condition de
ned a lack of key, which was included here
as a control condition. The stimuli were ordered such that all tonal stimuli were
used an equal number of times, and the conditions appeared in all permutations
equally in order to control for order effects.
Each stimulus consisted of 16 isochronous events lasting 500 ms each, with each
stimulus therefore lasting 8 s without gaps in between. Each event consisted of a
chord recognised in Western tonal music theory, with each chord being in root
position (i.e. the lowest note of the chord is also the fundamental note). The sense of
key, or lack of it, was given by the sequence of 16 chords, rather than by individual
chords. For a single run, stimuli were ordered into twenty-four groups of three
stimuli with no gaps between stimuli or groups. The
first stimulus in each group was
always a tonal stimulus presented in the home key of C major, and the second was
always a tonal stimulus that could either be in the distant key of F# major, the closely
related key of G major or the same key of C major. In order to reset the listener
s
sense of relative key, the third stimulus in each group was always an atonal stimulus,
that is, the chord sequences without any recognisable key (Fig.
1.7
).
In order to draw the attention of the participants to the tonal structure of the
stimulus stream, the behavioural task in the scanner was to click the left mouse
button when they heard a change to a different key (
distant
,
close
and
initial
'
Fig. 1.7
Musical scores representing the stimuli used in the tonal experiment. At the top, stave is
the tonal stimulus in the key of C major, which is the initial and same conditions, respectively. In
the middle is the stimulus in the key of F# major, which is the distant condition. At the bottom is
the stimulus in no obvious key
