Digital Keyboards Synergy Preservation Page

Digital Keyboards Synergy Preservation Page

Digital Keyboards Synergy Preservation Page

Digital Keyboards Synergy Preservation Page

I’d like to light a fire under the entire industry right now…
I don’t want people to be so complacent about this.
We’re really lying back and being satisfied with trivial crap like
sampling machines. Not that they’re bad… But it’s musique concrete done
in a new way. It’s back to the ’40s and ’50s. That’s all it is. There’s
nothing wrong with that, but it’s not a breakthrough. It’s a refinement.

– Wendy Carlos, Keyboard Magazine, November 1986

This page is devoted to information and projects about one of
the most sophisticated synthesizers ever
made, the Digital Keyboards Synergy, and its offspring, such as the
rare Mulogix Slave 32, and its predecessors, such as the extremely rare
Crumar GDS.

If you have a Synergy,
it’s worth preserving. One tech I talked to estimated that
probably less than 100 (of the 700-800 originally made) are still in
Slave 32s (essentially a rack-mounted synergy)
are much rarer still; only 25-30 were made.

The Synergy has 32 digital oscillators that are allocated to notes as
they are played; voices which use more oscillators per note have less
polyphony. Each oscillator can play a sine or a triangle wave. The Synergy
is primarily known as an additive synthesizer, but you can also do FM on it
(although to avoid ticking off Yamaha, Digital Keyboards didn’t make a
big deal about that feature at the time.) It seems underpowered compared
to later additive synths, such as the brilliant Kurzweil K150, which has a
bank of 240 oscillators. Yet, the Synergy often sounds just as impressive,
if not more. I think that’s primarily for four reasons:

  • On the Synergy, you actually specify two complete sets of rates and
    breakpoints for the envelopes, and the Synergy can smoothly interpolate
    between the two based on, for instance, velocity information. On something
    like the K150, the velocity has much more limited control. This is much
    more complex than a simple crossfade.
  • On the K150, each partial can be set to non-harmonic frequencies, but
    each partial is then locked to that frequency. On the Synergy, each partial
    can have its own independent frequency envelope.
  • The envelopes are quite flexible, with up to 16 stages, for both
    amplitude and frequency. (The Kawai K5000
    had only give 5 stage envelopes.)
  • Wendy Carlos went nuts on the Synergy, and spent years refining
    its voice library. Most of her voices only use two or three oscillators, yet
    they sound incredible. The fact that she tuned them all by ear
    i.e. no FFTs or phase vocoders used! – is remarkable.


Photos of the Inside of a Synergy, and Debugging

I believe this is the only place on a web where you can find such photos.
I also include some repair tips (it took a while to get my Synergy fully
working, and I learned a lot in the process.)


Synergy/Slave 32 Software


Synergy Schematics

Synergy Mailing List

Yahoo Synergy-Synth:
“This group is for discussion of this instrument
in all its facets: design, repair, modifications, wants, tech tips,
upgrading from the basic unit to the II+ Kaypro version, voicing,
sequencing, basic operation and so on. This will be a moderated list for
smooth operations.”


Synergy Family Owners List

If you have a Synergy, Slave 32, or (gasp!) a GDS, please drop my a line
with whatever info you’d like to include here. Let me know how long you’ve
had it, what goodies you have, how you use it, etc. It would be nice to
get a feel for how many Synergies are out there.

The Sounds

What does it sound like? The
various metallic percussion instruments – vibes, xylophones, etc. – are the
most impressive on this beast.
They have a complex overtone structure that you just
won’t get by filtering a sawtooth. There’s a drumkit that’s mindblowing
considering how it’s being generated. The organs and brasses are fantastic
The strings are a mixed bag; they sound a lot better on Wendy Carlos’
recordings than they do right out of the Synergy. The bow scrapes are
impressive, but the strings overall sound
bit cheezy, coming out solo straight from
the Synergy; I suspect that on the recordings, Carlos is
making very careful choices of reverb and EQ, as well as carefully layering
them with other instruments. (Definitely, owning a Synergy isn’t going to
make you sound like Wendy Carlos any more than owning a Stratocaster will
make you sound like Eric Clapton.)
The pianos won’t fool anyone; it’s clear that you need a lot more partials
to pull off a piano (as the Kurzweil K150 does quite well.)


These are scans of the documents Mark Glinsky (check out his
Manual Manor
if a manual exists, he probably has it!)
sent me along the the Synergy
II+ he sold me. If you have other Synergy/MuLogix/GDS
documents, and can send me
either PDF scans or a hardcopy, please get in touch with me. I’d like
to make this section as complete as possible.

The next two documents are
different printings of the same document; I include
them both for historical interest.

Documentation from other sources:

Magazine appearances: (thanks to Ramiro Turin for sending these scans):

Circuit Layouts:

The Synergy is based on a digital synthesizer designed by Hal Alles when
he was at Bell Labs. This design is extensively documented in two journal

  • H.G. Alles, “An Inexpensive Digital Sound Synthesizer,”
    Computer Music Journal, Vol. 3, No. 3, Fall 1979.
  • H.G. Alles, “Music Synthesis Using Real Time Digital Techniques,”
    Proceedings of the IEEE, Vol. 68, No. 4, April 1980, pp. 436-449.

Essential Listening

  • Wendy Carlos,

    reviews, and
    Wendy’s commentary
  • Wendy Carlos,

    and the Beast

    reviews, and Wendy’s
  • Wendy Carlos, soundtrack to
    Wendy’s commentary)
  • Fred Becker,
    Inner, Stellar
  • According to Ramiro Tunin, Christopher Franke used his GDS
    on the “Thief” Tangerine Dream soundtrack, particularly preset 12
    (“Xstrings”), and Klaus Schulz used his GDS exclusively on the rare album
    “Dig It” on the “Brain” label
    (Side 1: 1. Death of an Analogue, 2. Weird Caravan,
    3. The Looper Isn’t a Hooker; Side 2: 1. Synthasy), recorded between
    May and September in 1980.
  • (added 6/07/09)
    John DeRosa spotted a Synergy in the video to Hall and Oates’s “Say It
    Isn’t So.” I have no idea if it was used on the actual recording or is just
    a prop for a video, but the sound does sound like something the Synergy
    could do.
  • (added 3/28/12) Kat Epple,
    who used to be one half of the group Emerald Web, noted that the Synergy
    was used on the Emerald Web albums Traces of Time, Nocture, Lights of the
    Ivory Plains, Dramspun, Catspaw, and Manatee Dreams of Neptune, some of which
    available from CD
  • Anyone know of recordings by other artists where it was used?

Synergy Links

Price Info

How much did you pay for your Synergy? They’re very hard to price.
I paid $850 for mine (II+, along with Kaypro and editing software). To
someone who knows what they are and how important they are in the history
of synthesis, they’re worth a lot; but such people are probably rare. I
heard of a II+/Kaypro setup going for $1500+shipping in the summer of 2005.


Projects that might be fun for someone to try:

  • Make some modern Windows/Mac software to send voice data to the Synergy
    over RS-232 (I’ve been looking for a DB-25 style
    RS-232 interface for the Mac)
  • Make a graphical Synergy voice editor (maybe Java would be good for
  • Design and prototype a new replacement DAC card, or a SPDIF interface
    card for the digital oscillator, to get pristine digital signals out of
    the machine
  • Make an FPGA replacement for the digital oscillator board. The
    digital oscillator board is around 110 TTL chips – I bet you could fit it
    in a modern Xilinx or Altera FPGA pretty easily.
  • Create a procedure for rack-mounting a Synergy. It looks quite doable;
    I’d just be hesitant to hack up my only working Synergy.
  • It would be feasible to grab some Z-80 simulator code, add code to
    simulate the front panel interface and the memory-mapped hardware, and
    actually run the original Synergy operating system on your PC. That would
    be pretty wild. Some folks are doing this for the
    Wave PPG 2.3,
    simulating the 6809 and all its peripheral chips

The technical documentation for the Synergy is quite detailed, so I think
all of the above projects are feasible.

If someone is interested in contributing to such projects, please pop
me an e-mail!


Before you try finding a repair shop for your Synergy, check out my
debugging tips on the
photos page. If you’re still stuck, you might try the

  • If he’s available, Paul Schreiber
    is probably your best bet. He owns a Synergy, so if you
    can nail the problem down to a specific board, you can just send him
    that board (avoiding the cost of shipping the whole thing, which weighs
    something like 75 pounds). However, Paul’s time is mostly taken up by the
    demands of his fantastic
    MOTM line.
    The last time I corresponded with him, he thought he wouldn’t be available
    to do any Synergy repairs until March 2005. But it wouldn’t hurt to ask.
  • Davidson Electronics wrotes:
    “We are quite familiar with these units and their architecture. It is best
    to send the entire unit to us.”
  • EPR
    wrote: “We have the stereo microscopes
    and surface mount work station needed to repair your [Synergy] unit to
    a stable and warrantable condition.”
  • David Vandenberg
    has created many Synergy modifications. He writes:
    “If anyone wants to send my their Synergy, I’ll be more than happy to try
    fixing it for them.”
  • If your keyboard is having issues, check out the
    Keyboard Upgrade
    Virtual Music.
    They also have assorted other
    spare Synergy parts. If you’re in Europe, they might be able to service your
    Synergy, as they service a lot of old synths, but I haven’t explicitly asked
    them.If anyone else knows of folks who can fix a Synergy, please let me know
    and I’ll add that info here.

    Last modified 1/31/2010
    Maintained by Aaron