[sdiy] MIDI to CV question - no Triggers?

[Michael Bacich]

On Mar 4, 2006, at 12:30 PM, D A F wrote:

> The Yamaha G50 apparently has three MIDI "modes":  "Multi-Channel",  
> "Single-Channel Polyphonic", and "Monophonic".

Ah.  I did not know those other modes were available.  Is this that  
old, late 1980's guitar synth with the very strange "guitar"  
controller that Yamaha made for only a minute, or is it the newer  
rackmount MIDI processor from around 2001?

If the G50 has a monophonic mode, that's probably the one to use.   
I'm sure that it will make a new MIDI note on every time you play a  
new note, whether or not you play legato or staccato.  You probably  
won't need to also have a trigger along with your gate -- the gate  
only should suffice.  This may depend on the type of envelope  
generator modules you're connecting to -- some require both gate and  
trigger to properly fire.  There are simple DIY workarounds for this,  
though.

> But that still doesnt answer the question of how the converter  
> interprets a sequence of events in which one note is on and another  
> note on is recieved.  I.E., how does it turn this sequence of MIDI  
> events into analog control signals?

If you're using it with a monophonic MIDI to CV unit, then your MIDI  
to CV should simply put out a CV and Gate for every new note that you  
play.  That is, if you first play a C note, it will put out the  
equivalent CV for a C note; if, on another string, you add another  
note to that C, making a chord that includes both C and E, the MIDI  
to CV unit should simply put out the CV for the new E note.  It will  
probably also put out a new gate with the E note (or continue told  
the gate open -- more on that later).

Some MIDI to CV units give you a couple of important options that  
relate to CV's and Gates for new notes.  They sometimes allow you to  
choose a note priority assignment, choosing between Low Note  
Priority, High note Priority, and Last Note Priority.  In your case,  
I would choose Last Note Priority, which would ensure that your most  
recently play note would be the one that comes out of the CV box.   
They may also give you the option for Single or Multiple Trigger.   
Both of these are useful, depending on the style of playing that  
you're doing.  Low and High Note Priority would probably be more  
useful when playing the CV box from a keyboard.  Without going into  
too much detail, know that the original Minimoog had low note  
priority, and the ARP 2600 had high note priority.

With Single Trigger, a new Gate will occur only if you release all  
currently held notes.  Otherwise, in the case of the aforementioned 2- 
note arpeggio (C, then E), the CV box will put out a gate and CV with  
the C note, but when you add the E note, it will only change the CV  
to E, but will not put out a new gate and retrigger your envelopes.   
This might be analogous to picking one note, then hammering-on to  
another note without re-picking -- the pitch changes to the second  
note, but the pick attack happens only on the first note.  If you  
think about it, I'm sure you can see how this type of CV/gate  
response might sometimes be useful.

With Multiple Trigger mode, the CV box will always issue a new Gate  
with every newly received MIDI note, whether you leave a space  
between the notes or not.  Usually, the CV box achieves this by  
turning the Gate off for a few milliseconds, effectively emulating  
what might happen if you paused between the two notes for a very  
short time.  This would be analogous to cleanly picking each and  
every note that you played on the guitar, no matter how fast you  
changed notes.  This mode would be very effective for certain types  
of playing -- for instance, if you were trying to emulate Al  
Dimeola's amazingly rapid right-hand technique, or if you were  
triggering a very short, percussive envelope which had no sustain,  
such as a drum sound or mallet sound.

Note also that the Minimoog provides only Single Trigger response,  
while the ARP 2600 has Multi trigger response.  This is not to say  
that one is more desirable than the other -- even if you have a  
preference of the sound of one of those synths over the other.  Both  
types of triggering can be useful for different musical effects.  In  
my opinion, both of these synths should have included a Single/Multi  
Trigger switch, but they unfortunately didn't.  (later-period  
ARP2600's with the duophonic 3620 keyboard may have such a switch --  
I'm not sure)

Most of the better MIDI to CV units give you these options for your  
CV and gate, which make it easier to interface with various types of  
synths, and easier to achieve the desired musical result.

What Scott G. said about slow MIDI response is true, especially for  
the Roiand units that have internal tone generators.  However, since  
your unit does not have an internal sound module and is MIDI only,  
you should probably expect no additional noticeable latency when  
using it with MIDI to CV.  In fact, if your G50 is that weird old  
thing with the space-age controller, you should get the same MIDI  
delay on low strings as you do on high strings, since it uses high E  
strings for each of its six strings.  The other types of "normal"  
guitar to MIDI converters have measureably slower response on the low  
strings.

Scott's warning about pitch bend is also important.  You may have to  
be careful to not bend notes, or at least to not bend when holding  
more than one note.  This will depend on how your MIDI to CV box  
handles incoming MIDI Pitch Bend data.  However, it's probably not  
going to be as big an issue with a monophonic analog system as it  
would if you were trying to control a polyphonic sound source.

Michael Bacich

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