Information Technology Reference
In-Depth Information
Fig. 12.17
The result from applying the pitch scrambling algorithm four times on the same input
order to illustrate this, let us assume an fMRI_index equal to 3. This gives a CS
value of 0.4.
Considering the same input measure as before (Fig.
12.14
) and the transformed
values from the
first pitch scramble shown in Fig.
12.17
, the value of
d
, between the
first scramble and the input signal, is calculated as follows:
d ¼ 74
71
f
ð
Þ;
72
71
ð
Þ;
71
74
ð
Þ;
71
72
ð
Þ;
71
71
ð
Þ
g
d ¼ 3
;
1
;
3
;
1
;
0
f
g
The scaled modi
er values are then calculated by multiplying the difference
values by CS = 0.4:
SMV ¼ 3
0
:
4
f
ð
Þ;
1
0
:
4
ð
Þ;
3
0
:
4
ð
Þ;
1
0
:
4
ð
Þ;
0
0
:
4
ð
Þ
g
SMV ¼ 1
:
2
;
0
:
4
;
1
:
2
;
0
:
4
;
0
f
g
Finally, the SMV values are summed with the values of the original input to give
a transformed set of output values:
New pitches ¼ 71
þ
1
:
2
f
ð
Þ;
71
þ
0
:
4
ð
Þ;
74
1
:
2
ð
Þ;
72
0
:
4
ð
Þ;
71
0
ð
Þ
g
New pitches ¼ 72
:
2
;
71
:
4
;
72
:
8
;
71
:
6
;
71
f
g
As before, pitch values are rounded up to the nearest whole number as per the
MIDI standard, giving a transformed set of pitch values equal to {72, 71, 73, 72,
71}, which is rendered as {C5, B4, C#5, C5, B4}, as shown in Fig.
12.18
. Note that
the output is signi
cantly closer in overall structure to the unscrambled input than
the
first scrambled transformation shown in Fig.
12.17
, with only the
first and third
notes having changed here.
Fig. 12.18
Transformed output created by pitch scrambling algorithm assuming fMRI_index = 3
