Synthesizer Magazin: Fender Rhodes ChromaBy Der Moogulator, Klanganästhesist
Translation by Christian Kleine 
This article, from the May-June 2008 issue of Synthesizer Magazin, is being reprinted with kind permission of the author.
The Chroma had a difficult childhood; its real father was ARP (originally "Tonus"), and the company burned the candle at both ends with this new synthesizer and its new concepts. In addition, the innovative Avatar model wasn't very successful (only 300 were built). So, ARP went bankrupt and Fender Rhodes/CBS was the new owner of the big, heavy Chroma. Two Korg MS-20s could easily fit on top of it. There was also an Expander version of the Chroma which, in 1982, was relatively futuristic. It would take another year until MIDI equipped synthesizers would hit the market; and the Chroma went with ARP technology and new Rhodes brand in a niche in which Rhodes wasn't previously known. The Chroma was ahead of its time with a semi-modular structure and memory system, and is more reminiscent of the Oberheim Xpander, which would see the light 2 years later, than the previous ARP models such as the 2600 and Odyssey.
The burning question: MIDI-fication...
Yes, it's possible; in fact, there were several vendors. In Germany, these were EES and Jellinghaus; today you can order the CC+ Interface from Canada [or Italy] and you get excellent MIDI implementation and SysEx dump functionality. There were approximately 3000 Chromas manufactured [or were there?], which is a good number but not really a success story. The DX7 or C64 make this number look almost laughable.
Chroma: The Concept
A bit unconventional, but aimed at a specific set of clients: the look and feel is clearly focused on "players," the Zawinul-like Rhodes players, musicians who play piano. Indications of this are the semi-weighted keyboard and the appearance of the housing. A company like Rhodes considered the Chroma to be portable because the keyboard had a range of almost five octaves. The housing was bulky and heavy. Knobs and switches have been eliminated in favor of a big flat top – this might be also part of the Rhodes philosophy. Also, it certainly was cheaper. In the mid eighties, Roland also demonstrated how to save money: selling knobs and synths individually because knobs were for programmers and the rest should simply buy presets? Not really: it was simply cheaper without knobs. That's the simple truth: the companies saved a lot of money in production and only the more wealthy musicians bought the programmers – currently, the programmers are often more expensive than the synthesizers. Back to the Chroma: on the inside, it doesn't look as conservative as it might seem. Unfortunately, until today the "player" type was rarely a passionate synth user; proof is in the (excellent) preset selection (there were lots of additional sounds available). The Chroma is a pure studio instrument and it needs time to get familiar with the programming and its interface. The programming concept is similar to a Korg Poly 800/61 or the newer Microkorg, although the latter has at least a few knobs. Besides the panel switches, you need to learn the routing of the modulation sources - they are only shown as numbers in the display which is not very intuitive.
The Chroma is equipped with 16 OSC-VCF-VCA chains, which can be connected as pairs. A single-oscillator patch can have 16 voices. As expected there are 8- and 4- voice combinations as well. Each chain has an LFO, 2 envelope generators, a VCA and a filter – all completely analog. Each chain can produce glissando or portamento with its VCO. This can produce very interesting effects with several VCO's and different portamento times. The waveforms are variable pulse, saw and white or pink noise.
The crux of the matter is the connection of chains and the so-called "modules" as a path. You can choose between serial, parallel or variable mixable paths with ring modulation, (oscillator) sync or filter-FM in a classical manner. The VCA's are usually placed after the filter with the exception of the "variable" mode.
The filters have 12db per octave and can be either high- or lowpass. As a pair, you can create 24db/octave filtering with bandpass, notch, or double lowpass functionality. The resonance of the filter has only 8 steps but ranges from self-oscillation to Kraftwerk-style "zapp" sounds. The LFO's are relatively slow (12 hertz is the maximum), but they have lots of waveforms and patterns (staircase-modes and sample/hold). The name for a Chroma LFO is "sweep generator." The speed can be modulated. Many parameters have a list of modulation sources but they are shown only as numbers in the display.
You have to either write down the 15 entries or memorize them. The VCA's have 2 modulation sources, the filter cutoff has even 3. The resonance can not be modulated but the LFO's in speed and intensity. Also, the envelope parameters attack and decay can be modulated. The keyboard is velocity sensitive and has aftertouch, which results in attractive possibilities. The envelope generators do not have a sustain, only DADR and ADR. The envelope generators aren't prepatched and are fine for short "blip" sounds but aren't extremely fast. The resolution of the parameters are usually 64 steps. Cut off and Pitch have bipolar modulation with 128 steps. Volume has only 16 steps and the envelope parameters 32 steps.
Modulation via touch can only be turned on and roughly adjusted in it's intensity - velocity is either activated or not.
Because of the independent oscillator glides, sync effects can be achieved via playing distant note values. The two oscillators reach quickly the pitch of the last played note and with activated glissando the pitch reaches in steps the actual value, the result is: distant note values create the "cutting" sound. The LFO`s have different trigger modes which is quite remarkable for its time.
As final look on the Chroma technology, a few last words about the "Keyboard algorithm." Behind this is a chord-memory, the arpeggiator or different key modes for the play order (mono/poly, last priority etc.).
The arpeggiator offers a random mode. The sequencer mode works more like an arpeggiator which memorizes the order of the notes played and plays these back in the same order. Also the dynamic of the notes played is memorized. The three equalizer-faders (bass, middle, treble) are unusual. Whether or not these are really necessary, I leave it to the reader to decide. You'll find four single outputs on its back with the possibility to change the output level for each and additional XLR-outputs. Pure luxury.
There's also a monster double-foot pedal as part of the package. The German manual is a bit weird but it explains the routings and clears the fact that not a completer chain can be used for ring-modulation but the ring modulator is hard-wired (with both VCO's of the different chains). Synth-users with a bit of experience will not need the manual, assuming the modulation and routings are known. They could be printed out and stuck on the housing. My tip in case you have no manual: Look into an software editor (Sounddiver). Editors aren't always usable, they depend on the retrofits and they aren't necessarily identical with the actual SysEx implementation.
A chip off the old block
The Chroma with computer interface predated MIDI in 1982 and Macs or the Atari ST weren't on the market: the Apple II/IIe was the computer of the day. It had a RS323 interface and editor software was available as well. This was the common machine, together with the Sinclair and the C64. Geeks used them for those kind of jobs and they still had the DIY air about them. MIDI interface manufacturers were Syntech, Chroma Cult, KMX, EES Wieschioleck, Kenton and JL Cooper with the Chromaface. Today, there's only the CPU plus (CC+) interface by David Clarke [21030085++] and Sandro Sfregola  which is technically the most advanced from all. It requires a transplant of the heart of the Chroma. It's compatible with the Syntech interface. It requires a transplant of the heart of the Chroma. It's compatible with the Syntech interface. Next to the RS323 interface on the back of the Chroma is also an optional slot, which is ideal to use for MIDI. The Syntech interface is also still available from the former Syntech employee Ken Ypparila .
If you made it this far, you only have to find software which will work with the Chroma. If you still have an Apple II, you can use ChromaGraph (LaBach/Kevin Laubach ) or the Chroma Music System. The latter is more a sequencer than a editor. All others might use Sounddiver, which has unfortunately been discontinued by Apple. There's also a Mixer-map for Cubase. The Chroma has a cassette interface as well.
If you want to listen to the "hard-bit-sound" of the 80's in a Modem remix, you can save your patches this old-fashioned way. You don't have to use a mono-recorder. If you don't have any of the mentioned solutions at hand, you can edit the Chroma with any SysEx controller (Mackie C4, Novation Remote SL etc.)
Input, Output, Out of Order?
Does it still work? If you ask yourself this question, just look at the display after turning on your Chroma. If you see an error message in the display, you could try to remove the voice cards and carefully re-seat them.
If it still doesn't work properly, you might check the power supply. If you want to check, repair or modernize your Chroma, you can replace the condensers, resistors and potentiometers and get great tips on the excellent Rhodeschroma.com site. The culprit is often the power supply, which originally was build for 100V/60Hz. This is a general rule for musical instruments developed in the USA (the author peers at the Matrix 12).
Monster in Monster's fur (or Synthi and Chroma are a minority)
As mentioned earlier, the Chroma is a quite heavy-weighted monster with a bit of unintuitive handling, although the previous parameter is called when you press a panel switch twice and a mechanism exists for editing identical parameters in different VCO-VCF-VCA chains. It helps a bit but it doen't replace a real set of knobs. Some parameter changes are audible with a click. It's certainly a bit more time consuming to edit the parameters in Korg Poly 800-style one after the other and always checking which modulation source can be identified with which number. Fortunately you don't have to dial a number but press a button and change its value then. Without any doubt it's worth the effort: the Chroma sounds really impressive. It doesn't only recall the ARP sound, it is an original ARP Synthesizer. Too bad that this was the last ARP synthesizer. Resonant sounds on the Chroma sound similarly solid and expensive as the Oberheim Xpander.
An alternative might be the minimalized Chroma Polaris. It's a bit easier to handle but does not offer as many possibilities. As mentioned earlier, the sound is excellent and comparable with the old ARP's, but polyphonic. Convincing and deep, inspiring sound can be expected. The filter and oscillators sound very voluminous and wide but not as "coloured" like e.g. the Moog - more neutral and always "expensive" – high quality.
The Chroma does certainly blow away almost all today's virtual analogues with one oscillator. It doesn't require any special user skills to do this – the sound does not thin out with high resonance and you can, similarly to the MS20, create nice sounds with an HP/LP filter combination. The vivid LFO modes certainly add enough life. The filter-FM sounds are also excellent and not cheap and thin. If there are distortions then only with full resonance – and it still sounds very musical. The Chroma is a wolf in wolf's clothing. If there's something to moan about, it's the missing knobs; but there's even a controller box which has been built by a Chroma-DIY-freak because the Chroma reacts to SysEx if you have a built in MIDI interface. Generally, this can also be done via the RS232 interface but the communication with the Chroma has to be at least partially decoded. Some other users made their attempt as you can see on the already mentioned site. Some PC application names are Windows interface/Window Chroma server – there's nothing in your way to experiment with the Chroma and your PC.
Final words, Summary, Keep your countenance
Owning a Chroma requires time, money, patience, and space in your studio. The handling is like it is and maybe prevents the Chroma price from exploding. The sound is excellent and rich. If the sound structure isn't complex enough for you, sounds can be split or used in dual mode but this results in 4 voice polyphony (or 7 if the 2nd sound is monophonic). It's not the multitimbral monster flagship but a big step for the ARP engineers and the lucky owner.
First versions of the Chroma still had the ARP logo on the boards. It uses CEM (Curtis) Chips. There are eight CEM3350 dual VCF and eight (in some versions nine) CEM3360 dual VCA's. CEM chips are not produced anymore and sadly their inventor recently passed away. The same chips were used in the "almost-moog" Crumar Spirit and in the rare Synton Syrinx. This means: The Chroma is definitely an exclusive instrument. The display is reminiscent of very old pocket calculators and is quite small, the display for the selected sound is much bigger.
Why all these details? You should only buy a Chroma if you really want it and if you like its sound. It's not a beauty and it's not fun to search for parts, but if it works, it might work for quite a while. The slow envelopes and LFO's are disappointing, but it never sounds boring. The Chroma might be, next to the already mentioned Oberheim Xpander, the best sounding CEM-based synthesizer.
I can't stop: It sounds great, partially better than others with similar components. It seems to be not only important which components are used but how they are connected.
The Chroma is not the only synthesizer with software based LFO's and envelopes – this only to prevent any misconception that software-based envelopes and LFO's are bad. It's easy to underestimate the Chroma. One of the arguments which speak for a Chroma is the polyphony and the warm, exclusive sound. In contradiction to some other ARP synthesizers the sound doesn't thin out with high resonance – in this context it's more a 2600 than a Odyssey even if this comparison does structurally fail. The standard for the sound is high; especially today's software-synth generation is not familiar with this kind of sound any more.
The Chroma is more a insider's tip of the synthesists than a classic instrument which can be named by every techno-kid. Generally I believe that the price might raise into similar heights as the Jupiter 8 did, a synthesizer known by almost everybody today.
There are no software alternatives; you might consider the ARP 2600 and Odyssey emulations or even better the Creamware/Soniccore-variations or the Plugiator by inDSP/Use-audio which is based on Creamware technology as well. It doesn't sound identical by far, the Chroma seems to do the job much better, especially filter-FM sounds more organic. The strengths of the Chroma are vivid pads, leads, and melody sounds. Bass sounds are also no problem. As on the Oberheim Xpander I would consider it for quality synth-pop. Its appearance isn't as cool as some others but if you're after good sounds and not gear porn, it's first class. If you like Boards of Canada melodies, you might have found a new love with higher quality.
Is the Chroma the messiah? Answer: Half way. You are in for a semi-perfect editor design with an excellent sound. It's a synthesizer which was way ahead of its time. It's certainly no modular synth – by today's standards – but it does its job very well. In my opinion it's superior to other heavyweights like the Prophet 5. This is up for discussion. Therefore there's the forum.
Special thanks to Klaus Fehls for the loan of the Chroma.
- Information about the CC+ Interface, schematics and tips can be found on the very informative site: www.rhodeschroma.com
- Other sites about Chroma and Chroma Polaris are: bluesynths.com, sequencer.de and the sequencer forum at http://www.sequencer.de/synthesizer
- Which chips are in which synths? The answer can be found in the synthWiki of Sequencer.de: Chips in Synthesizers"