| Some few keyboards, like the Kurzweil (who?) MIDIboard, will send
an aftertouch message stream for every note struck - poly aftertouch.
Other controllers, like the KX88, send just one message stream per MIDI
channel, generated by the finger pressing the hardest, I guess. I've
always equated this last 'mono' aftertouch with 'Channel' aftertouch,
in that there is one stream for all the key events happening on that
MIDI channel.
Rebuttals ??
karl
|
|
My Ensoniq SQ-80 does both types. Key pressure, or poly-aftertouch
does indeed send out a *separate* CC message stream for each note
you're playing. Channel pressure is indeed, as Karl pointed out, your
plain vanilla aftertouch. I believe if you look into the MIDI spec for
key pressure, there is a space in the header that identifies which MIDI
note number the message is related to, whereas channel pressure needs
no note number reference since all notes will receive the same. Good
way to clog up your MIDI stream (in fact, while Ensoniq touts key
pressure as a great feature, they recommend leaving it disabled unless
you are going to use patches that respond to it; see D-110 note for
disastrous side effects), but it can be *very* expressive.
The two types use different CC numbers (which ones...who knows?) and
many MIDI boxes don't recognize key pressure. More and more do, but
few boards send it; it's lots cheaper to implement the *response* than
to fit the keyboard with the sensors. This is hardly new, remember
when many boards wouldn't send velocity but could receive it?
On a wind instrument, mapping breath to aftertouch is to give you the
flexibility to control MIDI modules which don't know CC#2 (breath
control). Does anybody except Yamaha even send this CC? The most
common application would be to map breath to aftertouch as a volume
modulator, but it can be mapped to anything your SGU allows aftertouch
to map to....vibrato, filter, FX, you name it. I also believe that of
all the MIDI CCs, only key pressure is note-dependent; i.e. things like
sustain pedal, bend wheel, mod wheel, etc. are all global on the
channel.
As far as not having key pressure on the DH-100, remember that the
DH-100 only sends one note at a time. The distinction between pressure
types is moot on a monophonic instrument. Since the majority of SGUs
will not recognize key pressure, Casio's decison makes a lot of sense.
Brian
|
| Re: .3
I stand corrected. I checked 1293.9 for the list of MIDI CCs, and
you're right, aftertouch is not one of them.
However, Ensoniq sequencers (and likely others) lump aftertouch in with
the CCs when it comes to commands like "remove controllers".
Therefore, my misunderstanding.
Boy, this stuff is fun....
Brian
|
| re: the previous
Add the Roland A-80 to the list of controllers that are able to send
Poly Pressure (also known as key aftertouch and probably a few other
names). It does spew out a bundle of MIDI events. To give an example
of where it can be useful is to imagine a horn section part where you
want to each note (virtual horn) to have slightly different vibrato. I
guess it can sound more natural than having the exact same vibrato
added to every note.
As an aside, I've found that trying to play (with my mediocre ability)
a poly aftertouch patch with any sort of "repeatability" is extremely
difficult. I use it mostly in experimenting with the above vibrato-ish
effect but it's not something I've been able to vary my "technique"
around. When I've got sequencer disk space to burn, I'll record a
passage with the poly aftertouch on. Then play it back with and
without it. If I can fool myself into believing I can hear the
difference, sometimes I'll keep all that data in the sequence.
Otherwise, I use the version with the aftertouch stripped out.
- John -
|