Commodore Plus 4 - Page 188

176 Some Programming Techniques
3. Duration selects how long the note is played. The values in the duration
position can be from 1, which equals 1 / 60th of a second, to 65535, which is more
than 18 minutes. You can also use decimal numbers, variables, or calculations as
duration values but only their integer part will be used.
Use this formula to figure duration value:
Duration value = time in seconds x 60
When you are programming a song, the durations of all notes are relative to the
whole-note duration you choose. After you select the duration value for the
whole note, other note duration values are determined by fractions of the whole-
note value.
In this program, voices 1 and 2 are used simultaneously to play two-voice
harmony. Although a frequency value of zero does generate a sound, this pro
gram uses a value of zero to mean a rest (no sound).
Example: 10 VOL8
20 DIMN1%(66),N2%(66)rDl%(66),D2%(66)
30 1=0
40 REArai%(I)fDl%(I):IFNl%(I)<0TOEN60
50 1=1+1:GOTO40
60 T1=I:I=0
70 READN2%(I),D2%(I):IFN2%(I)<0THEN90
80 1=1+1:GOTO70
90 I1=-1:I2=-1
100 IFDl>0mENl30:ELSESOUNDl,Nl,0
110 11=11+1:IFIKT1THEND1=D1% (II) :Nl=Nl%(Il) :ELSE180
120 IFNl>0THENSOUNDl,Nl,300
130 IFD2>0THEN160:ELSESOUND2,N2,0
140 I2=I2+1:D2=D2%(I2):N2=N2%(I2)
150 IFN2>0THENSOUND2,N2,300
160 D1=D1-1:D2=D2-1
170 FORI=0TO80:NEXT:GOTO100
180 VOL0
190 DATA0,1,685,1,770,1,810,1
200 DATA798,1,685,1,798,1,834,1
210 DATA810,2,854,2,755,2,854,2
220 DATA770,1,685,1,770,1,810,1
230 DATA798,1,685,1,798,1,834,1
240 DATA810,2,770,2,0,4
250 DATA0,1,854,1,810,1,854,1
260 DATA770,1,810,1,685,1,739,1
270 DATA704,2,770,2,834,2,864,2
280 DATA864,1,834,1,798,1,834,1
290 DATA739,1,798,1,643,1,704,1
300 DATA685,2,739,2,810,2,854,2
310 DATA854,1,810,1,770,1,810,1
320 DATA704,2,834,2,834,1,798,1
330 DATA739,1,798,1,685,2,810,2