[sdiy] Yamaha DXy DCO's

[Peter Grenader]

I've realized any sound with harmonics can be filtered nicely- even one's
favorite sound - one may be surprised.  Whether its coming from digital
analog, your pet,  etc.

Onto semantics -  Is not a DCO a 'Digitally Controlled Analog Oscillator'?
Sounds like Phil did a real-live digital oscillator which is a different
animal.  The filtering , which knowing Phil's work probably sounded WAY
better than Yamaha's is attributed to the nature of digital VCOs being
controlled by digital EGs.  Precision being the key and the very reason this
type of thing is impossible with Analog components, because this level of
tracking can't be had.  Not to the point where phase cancellation creates
filtering effects.

The same kind of deal this possible with the Analogue Systems six voice
digital polyphonic oscillator.

Now, not trying to stick up for Yamaha, BUT it's the manner in which they
incorporated polyphony which gave these instruments their trademark thin
sound - which I believe is actually cycling through single pitches at an
incredibly fast rate.  Also bare in mind (and this goes down as the saddest
moment in the biggest deal in synth history) the machine at Stanford they
bought the technology rights for consisted of something like 256 operators
(digital VCO/EG pairs) on one side, and 256  sound modifiers (filters among
other things) on the other .  They just elected to squish that down to 6
operators and no sound modifiers.  It wasn't until later they they released
FM based machines that had these effect modifiers in them.    With
someth9ing like 500,000 DX7s sold, it surely wasn't a bad decision on some
levels, but for us tweek geeks....

- P


Cynthia Webster wrote:

Hi Phil!

The recent thread comparing DX7 and Buchla FM synthesis
techniques pondered the use of Analog Filters on Digital
FM Oscillators as something worthwhile to play with.

This reminded me of the experience that I had when
you brought your Yamaha DCO board to a SciSound
meeting.  I was rather amazed at the quality of the sounds
when no filters at all were involved.

Being a total filter junkie myself, I was humbled by the
filtered types of sounds that you were getting without any.

So naturally, I would love to hear that wonderful DCO
combination through a juicy analog filter like the (4-pole)
Nyle Steiner design!

Maybe we'll finally get to try this at Jim Patchell's next
DIY meet?  (March 27th same location as last year)

It is so odd that folks with fairly large systems typically
seem to dedicate only a single filter to each "voice"
(when it get far more interesting when multiple filters
are involved) 

Clever use of Digital Oscillators suggests that if some
of the "filtering" is done without filters...
then some total magic may be possible when they're
combined with um, (forgive me)... The real thing!

There are some keyboard synths that combine the two,
anyone care to share their experiences here?

Cyn




on 2/17/04 12:26 PM, phillip m gallo at philgallo at attglobal.net wrote:


Posts regarding polyphony so far have only dealt with multiple "like" voice
channels.   There is more to polyphony than implementing this way.
Polyphonically driving multiple "different" voices  is a very potent
technique.  It does require a more sophisticated "Note control".

As an example, in my pre-MIDI days, i built a controller which drove 9
Yamaha DXy DCO's with my SDIY modular tracing the highest key (descant) ,
and my MG-1 tracing the lowest key(basso).  The DXy's where given all notes
but even here i did not program the DCO's to have the same voice.  This was
a digital implementation of what i had done in an analog way with a
Lancaster Poly and the two synths.

This technique provides a really interesting ensemble effect that resulted
in two "performance" characteristics:

1) 
You playing stop's being pianistic or organ-tuan but becomes very precise as
notes allocate to "voicings" and repeatability requires precise technique,

2) 
Alternatively, pianistic playing resulting in very cool ad hoc voice
assignment which provided a "uncertainty" to the "orchestration" which had
the dangerous side effect of keeping you playing the synth way past bed time
and bending your orchestrational "ear".  Reminded me of the insite gained
from playing a "prepared piano".

Now MIDI make all this very easy.  Your M2CV needs to have rules in it for
not to voice assignment, an example being how to detect new voice
activations vs. "overlap" between key activations.  Since MIDI provide
velocity information as well as channel info it's pretty easy to make
decisions as to voice allocation.  You do need to provide a buffer for key's
pressed but not presently assigned to help govern these rules.

I have always disliked the rotary note assignment that poly synths often do
and am sure this is a major contributor to polysynths sounding like really
neat but non-the-less organ-like instruments.

regards, 
p 

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Grant Richter
Sent: Tuesday, February 17, 2004 10:37 AM
To: Rainer Buchty; Andalong Dudigual
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] poly?

> Now for the fake solutions:
> 
> The cheapest way to turn a monophonic synth into some sort of
> polyphonic machine is the arpeggiator. Works nicely with chords, but
> is rather unusable for true polyphonic play.

My electronic music teacher (Dr. August Wagner) pointed out that echo
devices like the Echoplex allow you to achieve polyphony with a mono-synth
by layering in real time. It was one reason they were so popular to use with
early synths. 

He also pointed out that electronic instruments are the only ones without
inherent acoustic ambience, which all acoustic instruments have. Hence
electronic reverb is practically an essential for imitative synthesis.

This was in response to my comment that using effects units with
synthesizers was "cheating". His response was that, not only was it not
"cheating", but imperative for the above reasons.

I know that is not what the original poster intended. But I thought they
were rather keen insights on his part (and for 1976). He died very young,
and I try to keep his memory alive in some small way.