Yamaha QX3 Manual page 15

Setup Notes, Continued.
Processor 2 sends a program
change (9) and volume
com-
mand (07, 55)
to
the last four
modules of the TXB I 6. This
is the sound that is being
played by the left hand
on
the
lower half of the KX88. The
lower half of the KX88 is
transmitting
on
MIDI channel
2, so the Channel Filter is set
to
accept only messages that
appear
on
this channel.
Again, all of the messages
on
channel 2 are recognized
except for Polyphonic
Aftertouch. The Data Modi-
fier is used
to
transpose the
voice up three octaves, and the
processor is set
to
output
on
MIDI channel2.
Processor 3 sends a program
change (I I) and volume
com-
mand (07,46)
to
the DX7 II.
Notice that the Channel Filter
is set to receive messages
on
MIDI channel2, so the DX7
II will also be playing parts
from the lower half of the
KX88 keyboard. This is a
good
example of how the
MEP4 allows you
to
use more
than
one·
tone generator
to
play the same part. The Mes-
sage Filter of processor 3 is set
differently than
that
of the first
two processors. In addition
to
filtering out Polyphonic
Aftertouch, the processor is
filtering out Control Changes
(the ' ' ' ' means that all
Control Changes are ig-
nored). The reason for this is
that processor 4 wiU be used
to
modify Control Change mes-
sages for the DX7 II. The
Data Modifier moves the
voice up three octaves, and the
data is sent out
on
MID I
channel3.
Processor 4 is normally
reserved for the sampler in my
setup. Since the sampler isn't
being used here, the processor
is being put
to
a different use.
Once again, the Channel Fil-
ter is set
to
receive only chan-
nel2. The Message Filter only
recognizes Control Channel
messages. The Data Modifier
then offsets the volume mes-
sage (Bn, 07) by -20, and
the processor sends data out
on MIDI channel 3. Basic-
ally, this setup is used
to
keep
the
DX7
II's volume mixed
down in relation
to
that of the
last four modules of the
TX8I6.
MEP4
Continued from page 13
Transposing Voices
In live performance, you are often forced to
play parts on the lower part of the keyboard
that, ideally, should be located on the upper
part of the keyboard. For instance, if there is a
fairly busy right hand part that has to be played
at the same time as a high string line, the string
line will end up being played by the left hand on
the lower part of the keyboard. Unless you want
that high string part to sound like a 'cello part,
you will have to transpose the string voice. In
addition, if you want to use the same string
voice with four different transpositions during a
show, you would need to store four different ver-
sions of the same sound for each affected tone
generator.
The Data Modifiers in the MEP4 can take
care of this problem. This sort of change is very
simple, but requires some knowledge of MIDI
messages.
If
you normally go glassy-eyed when
dealing with technical things, don't panic. You
can save yourself a lot of time and work by
learning just a few of the most useful messages.
In order to transpose a voice, you need to
modify a MIDI Note On message. This message
consists of three bytes (bytes, bits, and all of
those other computer terms aren't really impor-
tant to the musical applications we are talking
about here-The MEP4 owners manual explains
most of these terms if you would like to know
more about them). The Note On message looks
like this:
9n,xx,yy
The first byte- "9n" -is called the status byte.
Very simply, the "9" says that "This is a Note
On message," while the "n" represents the
MIDI channel that the message is in. The first
data byte- "xx" -corresponds to the MIDI note
number: It tells the tone generator which note
to play (and is the byte we will want to change
to transpose the voice). The second data byte-
"yy"-indicates how hard the note is played,
and is called the velocity byte.
With the MEP4's Data Modifier, you can
use the Offset feature to add or subtract a fixed
value to either "xx" or "yy."
If
you Offset the
"xx" byte (the MIDI note number) of a Note
On message, you will transpose the voice.
Now, here comes the payoff of this little
MIDI lesson. In the case of our string line exam-
ple, let's say we want to transpose the voice up
three octaves. Since adding 12 to a note num-
ber will move it up an octave, we can transpose
a voice up 3 octaves by setting an "xx" Offset of
+
36.
[NOTE: Not all keyboards use the same
system of sending Note Off messages.
If
you run
into a problem with the dreaded stuck-note syn-
drome, you may have to use one of the MEP4's
other processors to offset the Note Off
messages.]
You can also use the idea outlined above to
offset volume. The Data Presetter sends a one-
time-only volume command when an MEP4
program is selected, but if you move a MIDI vol-
ume pedal, all of the tone generators will jump
to the same volume. Normally, you will want
one tone generator to have a lower volume than
the others. The tricky part is keeping the proper
mix as you change the volume with a MIDI vol-
ume pedal. By applying a volume offset with the
MEP4, you can do this.
The MIDI message for volume is as follows:
Bn,07,yy
The status byte-"Bn"-says that "This is a
MIDI Control Change message." The second
byte-"07"-indicates that this message will
control MIDI volume. The final byte-"yy"-is
the data byte, and its value will be determined
by the position of the volume pedal. The possi-
ble values for "yy" are 0-127.
By offsetting the value of "yy," the MEP4
can control the relative volumes between tone
generators.
If
you Offset "yy" by - 20 on one of
the processors, for instance, the MEP4 will
always subtract 20 from the current volume
pedal position. Whichever tone generator is
affected by this will consistently be playing at a
lower volume relative to the other tone gener-
ators. Once again, this saves you the effort of
individually modifying the volume of the
patches within the tone generators themselves.
Beating
MIDI
I like to think of the MEP4 as a sort of MIDI
"Swiss Army Knife." The above examples only
begin to suggest the possible uses of the MEP4,
but they do describe some of the uses that I find
most valuable in live applications. As MIDI sys-
tems grow, they have a tendency to become un-
wieldy: They create restrictions that make it dif-
ficult to do all of the things you expect to be
able to do. The MEP4 can help you overcome
these restrictions, so that you can make the
most efficient use of your system.
Vol. 3 No. 8/ AITERTOUCH
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