Kurzweil K150 - APPENDIX 1 Appendix page 4

30ms
0
800 dB/s
-16
-32
dB
-48
-64
3200 dB/s
-80
2400 dB/s
-96
0 50
The K150FS operating system considers a host of variables in setting the absolute second breakpoint amplitude of each
partial when a note is started (actually it is setting the slope away from the first breakpoint). These include the attack
function table to be described, the MIDI velocity, the overall loudness of the model, the MIDI volume controller, and the
"graphic equalizer" layer parameters in the sound program. However, once the contours are launched.from the second
breakpoint, their evolution is predestined except for the Release Rates to be discussed later.
The Attack Function is a rectangular array with columns corresponding to partials and rows corresponding to attack levels.
Each attack level specifies a different spectral modification of the model. A particular attack level is selected according to
the MIDI note-on velocity. There may be as few as one or as many attack levels as desired and they can be arbitrarily
spaced. The entries in this main part of the attack function array are absolute amplitudes of second breakpoints. A zero entry
will suppress the corresponding partial in notes played at the corresponding attack level.
An additional row in the Attack Function gives the times of the second breakpoints, one for each partial (column). An
additional column specifies the MIDI velocity (after translation to amplitude according to the current velocity map) for each
of the attack levels. The last array element at the extra row and column intersection gives the earliest second breakpoint time
which is when interpretation of the update command list should begin.
To make it easier on the processor in the K150FS, the second breakpoint times in the additional row are given as a special
code, not in milliseconds or samples. The codes are drawn from the following table:
TIME CODE TIME
2 53
3 54
4 0
5 55
6 1
8 2
10 3
12 4
14 5
16 6
18 7
Note that only those times listed in the above table are available for the second breakpoint time. The Sound Modeling
Program rounds off the second breakpoint times when a model is compiled but retains millisecond accuracy for the third and
succeeding breakpoints. In cases where the user specified second breakpoint time is greater than 250mS, the .S.M.P.
actually inserts a phantom second breakpoint during compilation at 250mS that resides on the line segment connecting the
user specified first and second breakpoints.
Below is an example of an attack function for the earlier 3 partial example with 3 attack levels. The middle attack level,
which is used when the MIDI velocity maps into a loudness between -12 and -6dB, specifies the model unaltered. The
highest level, used for loudnesses above -6dB, has the first partial left alone but the second boosted by 3dB and the third
boosted by 6dB thus making the sound brighter. The lowest level, used for loudness below -12dB, cuts the third partial by
3dB while leaving the first and second alone.
Original Contour
Second BP shifted
down 16 dB.
200ms
-240 dB/s
100 150 200
msec
CODE TIME
20 8 55
22 9 60
25 10 62
30 11 65
32 12 70
35 13 72
40 14 75
42 15 80
45 16 82
50 17 85
52 18 90
200ms
-200 dB/s
250 300 350
CODE TIME CODE
19 92
20 95
21 100
22 105
23 110
24 115
25 120
26 125
27 130
28 135
29 140
Hardware clips
at -95.6 dB
400 450
TIME CODE
30 145 41
31 150 42
32 160 43
33 170 44
34 180 45
35 190 46
36 200 47
37 210 48
38 220 49
39 230 50
40 240 51
250 52