Commodore VIC-20 Programmer's Reference Manual page 118

MUSICAL NOTE VALUES
The accompanying chart shows the two values to modulate
between to get the "true" note in the first column. Using the
program in Example 3 above, POKE the lirst value, then the second
value in line 100 to get the "true" modulated tone.
I
NOTE
C
C#
D
D#
E
F
F#
G
G#
A
A#
B
C
C#
D
D#
E
F
F#
G
G#
A
A#
B
C
C#
D
D#
E
F
F#
G
G#
A
A#
B
VALUE 1
131
140
145
151
158
161
166
173
178
181
185
189
192
197
200
203
206
208
211
214
216
218
220
222
224
226
227
229
231
232
233
234
238
237
237
239
VALUE 2
162
167
174
182
186
190
195
207
209
212
219
221
223
228
235
236
238
102