[net.music.synth] DX7 and ability to split

tim@fisher.UUCP (Tim Snyder) (01/23/86)

> discussion with a salesperson. They tell me that splitting the
> DX7 is not easy. What I want to do is program the left side of the
> split for bass and the right side for all the other stuff.  The

> 			
> 						Thanks,
> 						Frank D. LaRocca
> 						homxa!fdl
> 						201-536-0582

Briefly (and simply, for the uninitiated):

The DX-7 uses "algorithms" composed of "operators" to form its sounds.
An operator can be either a "carrier," which is an actual sound produced
by the algorithm, or a "modulator," which modulates or "wiggles" a 
carrier's sound.  Many of the algorithms have more than one carrier, 
(two to six) hence can produce two very different tones simultaneously.

The DX-7 has no DISCRETE split.  One uses "scaling" to achieve this as
follows.  First, an algorithm such as the one mentioned above is chosen
and the two required tones are programmed to two carriers.  Second, an
arbitrary breakpoint is chosen.  Third, the two carriers are scaled so
that one essentially appears only to the left of the breakpoint, while
the other appears only on the right.

The scaling is done as follows.  Before any scaling is done, a carrier
is uniformly activated by the entire keyboard, hence both sounds will
occur simultaneousy over the entire keyboard.  To place a given carrier
(say the one doing bass) to the left of the breakpoint, one chooses
to assign a negative "curve" to the portion of the keyboard to the right
of the breakpoint.  Either an exponential or linear curve can be selected.
The linear one is used to achieve a split, and its value is maximized
so that the carrier's sound dies away rapidly to the right of the break-
point.  Similarly, the other carrier is made to disappear to the left
of the breakpoint, giving the desired split.

Since the split is not discrete, there is a "fuzziness" near the break-
point, i.e., a bit of, say,  brass might occur to the immediate left of it and
some bass might be heard to the immediate right.  I don't find this to
be a problem since only a few keys are affected, i.e., one can make the
carriers die away damn quickly if necessary.

In terms of the difficulty of doing this, it is no more so than
programming the instrument, which many find not so easy.  Given
the unbelievable range of capabilities, however, the programming 
is a relative snap.  

Also, since you are dividing an algorithm's carriers to produce two
sounds instead of one, you will not have the richness you would have
when using that algorithm to produce a single tone.

One does not have to start from absolute scratch.  You can take ideas
from your favorite bass patch to form your bass portion of the algorithm,
etc.   If you are doing bass all the time, though, it will take a while
to get rolling since you will have to "borrow" carriers from the patches
you wish to use on the right side of the breakpoint.

Yes, a TX-7 will help.  In addition to giving you the astounding sound
and flexibility of virtually two DX-7's, it will eliminate the problems
mentioned in the prvious two paragraphs.

BEFORE YOU BUY:
Find a knowledgable salesperson (one who owns and uses the instrument
for such things) to show you what is gained and what is lost when doing
this.

My feelings on the instrument:
...on the order of erections and coronaries....MONSTER!

                            Best of luck,
                              Tim Snyder
			      princeton!fisher!tim or princeton!tilt!tim