Atari XL

90
The Atari XL Handbook
up a series of numbers corresponding to notes but
we need a way of storing them. One way is to store
them in a string, reading them one at a time as
parameters for a SOUND command. This
technique is illustrated in the following program.
10 DIM TUNE$(ll)
20 TUNE$ = "QQQQDHHQQUQ"
30 FOR Z=1 TO LEN(TUNE$)
40 N = ASC(TUNE$(Z,Z»
50 SOUND 0,N,10,8
60 FOR D = ° TO 100:NEXT D
70 SOUND 0,0,0,0
80 NEXT Z
The main limitation with this method is that the
notes are all the same length, which renders it
impractical for all but the simplest music.
There are several ways of overcoming this: for
example, a second string could be used to hold the
data for the length of notes. Add these lines to the
last program to hear this technique in action.
15 DIM L$(ll)
25 L$="32132121214"
60 FOR D=O TO 100*VAL(L$(Z,Z»:
NEXT D
This method is adequate for simple tunes but a
better way is to hold information concerning notes
and note lengths in DATA statements like this:
10 FOR Z=1 TO 13
20 READ NO,LE
30 SOUND 0,NO,10,8
40 FOR DUR=O TO 100*LE:NEXT DUR
50 SOUND 0,0,0,0
60 NEXT Z
70 SOUND O,O,O,O:END