Volume Envelope; Envelope Number; Number Of Steps; Amplitude Of Step - AMSTRAD CPC464 User Manual

VOLUME ENVELOPE

The volume envelope command is env. This normally has 4 parameters: The last 3 parameters may
appear in any of up to 5 optional envelope sections available. We are only using one of these here.
Further explanation will appear in chapter 6.
env envelope number, number of steps, amplitude (size) of step, step time.

ENVELOPE NUMBER

This is the number given to a particular envelope so that it can be specified in the sound command.
The range of envelope numbers is 0 to 15.

NUMBER OF STEPS

This is used in conjunction with the step time. For example, you may wish to have 10 steps of 1
second each. In such a case the number of steps is 10. The range of step numbers is 0 to 127.

AMPLITUDE OF STEP

Each step can vary in amplitude from a level of 0 to 15 with respect to the last step. The 15 volume
levels are the same as those in the sound command. However, the step can be adjusted from -128 to
+127 so that you can not only vary the amplitude up or down in the obvious way, but can vary it by
using numbers higher than 15 to give some strange effects. The range of amplitude of step numbers
is -128 to + 127.
STEP TIME
This number specifies the time between steps in 0.01 second, (1/100th' s of a second) units. The range
of step time numbers is 0 to 256. The longest time between steps is therefore 2.56 seconds.
To experiment with the volume envelope, type in the following program:
5 e n v 1 , 1 0 , 1 , 1 0 0
1 0 s o u n d 1 , 2 8 4 , 1 0 0 0 , 1 , 1
run
Line 10 specifies a sound with a tone period of 284 (international a), lasting for 10 seconds with a
start volume of 1, and using volume envelope number 1, shown in line 5 consisting of 10 steps,
raising the volume of each step by 1, every 1 second (100 x 0.01 second).
Change line 5 in each of the following ways and then run each time to hear the effect of changing the
envelope.