Yamaha TX 816 Owner's Manual page 51

Every time you
press
a
key on
the
DX7,
a variety of
MIDI
signals are sent extremely
repidly to
the
TX816. These
signals
include Key On, Key
Off,
Key
Pitch,
Voice
Number, and
signals
for
all
the Functions such
as
Pitch
Bend,
Modulation Wheel,
Sustain Switch,
After
Touch,
and
so
on.
Sound
like
a
lot
of
informaiton
to
send
for
each
note,
especially
if
you
are playing
repid,
complex
polyphonic music. But
M
I
D
I
works
fast-
-the accepted
data treanmission
standard
for
MIDI
is
31 .25 kilobauds,
wich
means
31,250
bits
per second.
That's
fast
enough
for
the
most
rapid
changes
in
a
musical program
to
be handled with
ease.
What
happens
when
you
play
a
chord?
The MIDI
system separates out the notes
in
the chord,
and sends
the
MIDI
impulses
serially,
or
one
after
another. True, the music
is,
in effect,
cut
up
into thin "slices" of time,
but
just
as
in
a
movie where
a projection
speed
of
only 24 frames
a
second
appears
like
smooth,
uniterrupted motion, the
"slices"
of
time
are
way,
way
too small
for
the
ear to sperate
them. Machines
are
much
more
perfect
then people
and
this
is
exactly
why
the simple
MIDI
system
is
able
to
deal with the
most
subtle, expressive,
spontaneous music
that
you can
play.
The
31.25 kilobaud transmission
rate
permits
an extremely
useful
MIDI
feature--
the transmission
of
16 MIDI
channels
on
a
single cable.
Each
MIDI
signal
starts
with
a
MIDI
channel number.
This
signal
will
only
be
receibed
by an instrument
set to the
same MIDI
channel number,
or set to
Omni,
the
mode
that
permits reception
of
all
MIDI
channels.
In this
way
a single cable
may
be used
data
to sixteen instruments,
each performing
a different
musical
part.
This process
is
utilized
in
system No.4
in
the
SYSTEMS EXAMPLES
Chapter,
where
a
CX5
Music
Computer sends
eight parts of
music
down
a single
cable
to individually control the eight
modules
in
the
TX816.
"MIDI
Formatting"
is
the
phrase used
to
describe the
singais that
have been agreed upon
to indicate various functions
according to the "system
exclusive information" of the
Yamaha
series of
digital
music
devices. This format
is
not
necessarily
compatible with
other manufacaturers'
MIDI
devices, apart
from
the basic singais
such
as
Key On, Voice
Change,
etc.
Every time
a signal
is
sent,
it
usually consists of
more
than
one
byte.
For
Example,
the
Key
On
signal
uses three
bytes,
as follows:
t.
Key
On, which can be
notated as 1001nnnn.
This byte
is
also
known
as the Status
Byte, as
it
tells
the
M
I
Dl instrument the category
of
this signal,
and
is
The
Key
On
byte
is
separated
into
two
sections:
The
first
half,
1001
,
means
"a
key has been
pressed" according
to
the
MIDI
format.
The second
half gives the
MIDI channel number, from
1
to 16.
Autute
readers
will
notice that the
second
half
has only
for digits,
which
in
the binary system allows
you
to
express only
numbers up
tp 15.
However,
we
can
also express
a zero,
so
channels
numbers
1
thru
1
6
are
expressed
in
this
M
I
DI signal as
thru
1
5,
subracting
one
from the channel
number
for
the plurposes
of
transmission
only. This
is
commonly
done
in
the
MIDI
system.
2.
Note Number, which can be
notated as
Okkl(i(iil(.
This indicates the pitch of the
note.
MIDI
note
numbers
range from
to 127,
in-
cidating notes
C-2
to
G8
(-2
and 8
are
octave numbers).
This gives
a
range
of
over
10 1/2
octabes.
When
you
think that the
average grand piano has
a
range
of less
than
1
1
/2 octaves, the
MIDI
note range
is
more
than
enogh
for
any
musical
purpose.
3.
Note
Velocity,
which can
be
notated as
Ovvvvvvv.
The
velcity of the note
(which
is
another
way
of
saying
how
hard the note
was
hit)
generates
a
MIDI number
form
to
127 which
can be used
to
express the
volume
of the
note.
127
increments
is
more
than
enough
to express the
most
subtle
dynamics--if you can
imagine
a
volume
control with
1
27
divisions
on
it,
this
gives
you
an
idea of the
degree
of subtlety available.
Further explanation of
MIDI
will
not
necessarily help
you
to
use
this
system
better.
The whole
point
of
the
MIDI
system
is
to
make
digital
music systems easy
to as-
semble and
simple
to use,
by musicians
who
have
neither the time nor the
desire
to
acquire
a lot
of technical
knowledge.
However,
for
computer
enthusiasts
who
may
wish
to control the
TX816
with
in-
struments
of their
own
making,
or
instruments outside
of the
Yamaha
range,
this
manual
continues with
full
details fo the
MIDI
Format
of
the
TX816.
50