Your Commodore - Commodore Is Awesome

A
swhich
enables you to store any sound
oin
memory. Once stored in memory
uthe
sound can be manipulated in
n
various ways. Possibilities include,
d
speed variation, reversing the sound,
altering the pitch of the sound etc. You
s
could sequence the sound like a drum
amachine
or Paul Hardcastle's
m
N N N Nineteen, or just use the com-
pputer
keyboard as an organ, each key
lplaying
the sound at a different pitch.
e This program, written for the CI6
r and Plus/4, allows a sample of up to
itwo
seconds to be stored in memory.
s This takes up a staggering 10K of the
a computer's memory, so you can
pimagine
the problems getting all of the
r
o
g
r
a
m
C16 & PLUS/4 UTILITY',
C16 Sound
Sampler
lifilui isselli I
8-LOO
P
T O
S
T
A R
T
6
1
Now your C/a can really
sound like a trombone with
this excellent program.
By Gary Fry
program into the C16.
Two seconds? I hear you say.
This is actually quite a lot when
you think about it. Just count it to
yourself. Not many sounds take longer
than this, And don't forget once you
have sounds in memory you can
sample them to create much longer
sounds.
Sampling is quite easy to do since
the Commodore Datassette does quite
a lot of the work for you - it converts
the analogue voltages which make up
the sound on a cassette into digital
ones and zeros. These one's and zero's
are then transferred to the computer's
memory, just like a program when
loading.
YOUR COMMODORE november 1986:25
How It Works
In order to fill the computer's memory
with the necessary ones and zeros the
cassette port is read (memory location
0). A process called °Ring is then used
with each byte read in to read just one
bit from the number read in. By rotating
the number read and repeating
the process eight times, eight ones or
zeros are loaded in. This gives one byte
of sample. This is repeated until the
10K of memory is filled. You could
look at it like a cog wheel with eight
teeth 'feeling' 10 holes in a long strip of
paper. Each full turn of the wheel corresponding
to one byte being loaded.
Playing the SampleBack
This is much the same process as read-
ing from the cassette port, but this time
it is applied to the computer memory
where the sample has been stored.
When a one is read an audible sound is
emitted from the speaker; when a one
is read, an inaudible sound (too high is
made). This process produces a click.
Do this a thousand times in a frction of
a second, and your sound is built up.
In order to get the speed necessary
for this program the screen has to be
turned off during playback. This
makes the computer work at almost
twice normal speed.
Playing with a Sound
The organ/piano facility is probably
the best facility, this reproduces the