Number
of
Steps
This
parameter
specifies how
many
different steps of tone (pitch) you
want
the
sound
to pass
through
before
it
ends. For example,
in
a note which lasts 10 seconds, you may
wish to have
10 tone steps of 1 second each.
In
such a case,
the
<number of
steps>
parameter
used should be 1
0.
The available
range
of <number of
steps>
is 0 to
239.
Tone
Period
of
Step
Each tone step
can
vary
in
the
range
- 1
28
to + 1
27
with respect to
the
previous step.
Negative steps
make
the
pitch of
the
note higher; positive steps make
the
pitch
ofthe
note lower. The
shortest
tone period is
0.
This
must
be remembered when
formulating
the
tone envelope. The full
range
oftone periods is shown
in
the
chapter
entitled 'For your reference ....
'.
Time
per
Step
This
parameter
specifies
the
time between steps
in
0.01 second (hundredths of a
second) units. The
range
of
<time
per
step>
numbers is 0 to 2 5
5,
which means
that
the
longest time between steps is 2.56 seconds (0 is
treated
as
256).
Note therefore,
that
the
<number of
steps>
parameter
multiplied hy
the
<time
per
step>
parameter
shouldn't be
greater
than
the
<duration>
parameter in
the
SOU
N D
command, otherwise
the
sound will finish before all
the
tone steps have been passed
through. (In such a case,
the
remaining
contents of
the
tone envelope are discarded.)
Likewise,
if
the
<duration>
parameter
in
the
SO
UN
D command is longer
than
the
<number of
steps>
multiplied by
the
<time
per step>,
the
sound will continue after all of
the
tone steps have been passed through,
and
will
remain
constant
at
the
final tone
pitch.
To
experiment
with
the
tone envelope, type
in
the
following program:
HI
ent
1,1111111,2,2
2111
sound
1,142,2111111,15,,1
run
Line 20 specifies a
SOU
N D
with
a tone period of 1 42 (international
a)
lasting for 2
seconds
with
a
start
volume of 1 5 (max), without a volume envelope (represented by
a
blank
parameter,
,)
and
with
tone envelope number 1 .
Line 1
0 is tone envelope
number
1 consisting of 1
00
steps, increasing
the
tone
period (reducing
the
pitch) by 2, every 0.02 second (2 x 0.01 second).
Foundation Course
Chapter
'1
Page
73
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