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The E-mu mystery modules - updated.

(extracted from the E-mu Modular Synthesizer section of Zappa's Gear)

FZ took delivery of his custom E-mu synth in 1976. It was one of the largest and most complicated systems that they ever produced. It was built into two 4100 walnut system cabinets, each approximately 45” wide by 26” high; containing the following modules:

Cabinet 1:


1 × 2000

Voltage Controlled Amplifier

1 × 2010

Quad Voltage Controlled Amplifier

2 × 2100

Voltage Controlled Low-Pass Filter

1 × 2110

Voltage Controlled High-Pass Filter

1 × 2120

Universal Active Filter

4 × 2140

Resonant Filter

3 × 2200

Voltage Controlled Oscillator (sine/triangle/sawtooth/pulse)

2 × 2210

Sawtooth/Pulse Voltage Controlled Oscillator

2 × 2350

Dual Delayed Transient (ADSR) Generator

2 × 2355

VCTG (Voltage Controlled Transient Generator) Input Unit

1 × 2400

Noise Source

1 × 2410

Sample & Hold

2 × 2430

Ring Modulator

1 × 2451

Potpourri Module – Summing Amp/Low Frequency Oscillator /Digital Inverter/Comparator/Inverter

2 × 2455

Mixer (4 signal inputs, stereo output)

1 × 2800

Blank Panel

1 × 2905

2905 Power Supply with Keyboard Outputs

1 × 2906

2906 Multiple Panel (4×8 socket patch bay)

1 ×

Custom Output Mixer

1 ×

Unnamed module with 6 switches, 4 jack sockets and 8 trim pots. This does not look as if it was made by e-Mu as it uses different switches and jack sockets, which are poorly lined up.

1 ×

Unnamed module with 3 switches, 6 jack sockets and 6 balanced output connectors.



Cabinet 2:


2 × 2010

Quad Voltage Controlled Amplifier

12 × 2210

Sawtooth/Pulse VCO

6 × 2100

Voltage Controlled Low-Pass Filter

3 × 2350

Dual Delayed Transient (ADSR) Generator

1 × 2355

VCTG (Voltage Controlled Transient Generator) Input Unit

1 × 2510

8 Position Address Generator

1 × 2520

Voltage Source Output Unit (combined with the 2510 this made one of the world’s first sequencers)

1 × 2905

Power Supply with Keyboard Outputs

1 × 2906

Multiple Panel (4×8 socket patch panel)

1 × 4060

Keyboard Sequencer Output panel

1 ×

Unnamed module with 5 jack sockets, 11 control knobs (including 1 marked ‘Master Filter’ and one ‘Chorus/Normal’).

Also included were two 4000 mono keyboards, and the new 4060 Polyphonic Keyboard and Sequencer. The system was designed so that the two cabinets could be operated independently if required; Cabinet 1 as a traditional monophonic synthesizer with an extensive range of sounds and effects, and Cabinet 2 as a fully polyphonic instrument with its 12 oscillators and sequencer modules.

Towards the end of his life in June 1993, FZ donated the E-mu to the Musée de la Musique in Paris. The keyboards couldn’t be found when the synth cabinets were shipped to France, and by the time they turned up the museum had already built the exhibit and said that they had no room for them, so they were sold to a private collector.

However the two system cabinets are still prominently featured on the wall of the 20th Century music gallery. It seems fitting that they are in the company of various percussion instruments and two sirens which belonged to FZ’s teenage inspiration, the innovative composer Edgar Varese.

Three of the modules are unnamed, and the Output Mixer in Cabinet 1 looks like a custom unit. At least one of the others looks 'home-made' - E-mu would never have produced a module with such misaligned switches and connectors. See the pictures below for details.

Cabinet #1, highlighting the Output Mixer and two unnamed modules.

The 'Output Mixer' doesn't look like an E-mu product; from the lettering on the knobs (one for each guitar string) this must have been an interface to a guitar synthesizer/controller of some kind.

Mystery module 1 - note the misaligned switches and sockets. Who made it?

Mystery module 2 - some sort of input/output unit obviously, Tommy Mars thinks this may have been a custom interface for recording studio use.

Cabinet #2, highlighting the third unnamed module.

Mystery module 3 - Tommy Mars recalls this as being a master control for a bank of oscillators allowing them to be de-tuned to give a chorus effect. 

Update Jan 2012:

The following information was provided by Marco Alpert, E-mu sales manager for LA at the time:

'As for the modules, given the knobs labelled with the names of the guitar strings, the "Output Mixer" is almost certainly a dedicated output module for the voices controlled by the 360 Systems unit. I would normally doubt that it was built by E-mu, as we never used those knobs for anything, however the control labelling uses our standard font, so who knows.
I have no idea what module 1 is, but as you say, it's almost inconceivable that E-mu would build anything that looked like that, even as a one-off.
I believe module 2 is also associated with the 360 Systems controller (maybe 6 individual string-driven outputs?).
Module 3 is definitely not a standard E-mu module. Given that is does use the standard knobs, it could have been built as a custom module. From the labels I can read, it seems to have 2 VCO frequency modulation inputs, a pulse width modulation input, 2 initial pulsewidth controls and a filter (VCF) frequency control. I can't read the rest. Since there don't appear to be any controls for setting initial VCO frequency, it may be some sort of control module. (this ties in with Tommy Mars recollections).'

Alpert added the following comment:

'After just sending that first email, I had the distinct memory that the 360 Systems guitar controller that Frank used with his modular was some integrated unit, not 6 Slavedrivers. A bit of poking around on the web confirmed that prior to the Slavedriver, 360 Systems did in fact produce a (very expensive) polyphonic unit, of which only three were manufactured. I believe one of those was Frank's.'
I spoke to Bob Easton who produced the 360 Systems Guitar Synth controller that Marco Alpert refers to, and he told me:

'Frank used the polyphonic synth, but he never bought one, and as far as I know it isn’t on any album of his. The way he played is not very compatible with the “clean note” expectation of anybody’s converter—lots of percussive stuff. ... Maybe Frank used an Emu when dabbling with it; he had just bought a pretty large system.'

If any of you synthesizer buffs out there have any further information regarding the mystery modules please email me at