Comments
You can include reminders and comments
anywhere you like by using !! marks.
Anything written after a ! will be ignored
until the next ! or the " at the end of the
string is reached, eg
10 LET a$="abCDEFG!chorus!aCEaDG"
Channel selection
The command M is used to select which of
the three channels are in operation and
whether these give noise or musical tones.
You can have a maximum of three
channels in use at any one time, but it does
not matter whether they are all tone, all
noise, or a mixture of both.
Your choice is entered with a number
following the M, worked out like this
| Tone channels | Noise channels |
| A | B | C | A | B | C |
Number | 1 | 2 | 4 | 8 | 16 | 32 |
Mark each channel you want to turn on,
and note down its number. Then just add
them together to get the code you should
use after the M. For example, if you want
to use tone channels A, B, and C, you add
the numbers 1 + 2 + 4 = 7, so you use the
command M7. In the same way, M56
would turn on noise channels A, B, and C.
Noise can be used on any channel but
the most wide-ranging frequencies are
available in channel A. For the best results
put your sound effects in the string which
controls this channel - a$, the first string
after the PLAY command.
Controlling musical instruments
Whenever PLAY is running, a signal can be
sent to the MIDI port in the RS232 socket
at the front of the computer. This output
will drive any MIDI-compatible musical
instrument such as many makes of
synthesizer and drum machine, so that the
instrument will play the music which has
been programmed into the Spectrum 128.
Using the MIDI output lets you play
more complicated music with up to eight
notes at a time instead of three. All you do
is to follow the PLAY command with the
names of up to eight strings, (a$ to h$, for
example) each of which is constructed as
described above.
Do not try to send music to the MIDI
port unless you have already connected the
instrument (see page 3). To send the
output to the MIDI port, each string should
include the letter Y followed by a channel
number from 1 to 16. If you use the same
number in each string, up to eight notes
can be played by one instrument at the
same time. If you use different numbers,
you can control up to eight different
instruments at the same time.
Most MIDI instruments power up in
OMNI mode so that they play the notes on
channel 1 as well as the channel to which
they are directed. To get the notes on the
correct channels, the MIDI instrument
must be put into POLY mode. You can do
this by directly altering the instrument's
MIDI channel, or by including the
appropriate MIDI programming code in the
string. The programming codes for your
instrument should be listed in its handbook
and can be sent to it from the Spectrum
128 by including the letter Z in the string,
followed by the MIDI code number.
If your synthesizer understands key
velocity (so that the program you send it
controls the volume at which it plays) this is
interpreted from the V settings in the
strings. It is calculated at eight times the
volume set by the V command, so it takes
the values 0, 8, 16 ... 120. The key release
velocity when a note is switched off is sent
as 64. If the synthesizer is not designed to
understand key velocity, it will play the
same volume regardless.
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