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Keyfax: Rhodes Chroma Analog Polyphonic Synthesizer

By Julian Colbeck

The following article is being reprinted with permission from Keyfax Omnibus Edition: The real story behind the synthesizer revolution (see the Bibliography for more information).

Stellar synth company ARP crashed to earth in 1981, midway through the design of this instrument [see The Rise and Fall of ARP Instruments]. Both ARP and the Chroma were then picked up by CBS Musical Instruments and branded with the name of Rhodes.

The Chroma looks innocent enough, but it is a complex and intriguing instrument, offering a level of parameter interplay you'd expect only from an earlier, completely modular design coupled with a level of sophistication (velocity sensitivity and a direct computer tie-in) that you'd expect on an instrument five years down the line.

This was never, and indeed still is not, a synth for novices. In the right hands, it is capable of stunning subtlety and richness of texture. In the wrong hands, it'll simply get the user lost and bored.

The Chroma was one of the first synths to implement a form of digital access control (i.e., doing away with panel knobs and switches). It was also way ahead of its time in its ability to interface directly with an Apple IIe computer to run its own sequencing software and patch librarian. And all this before MIDI even entered the picture, though MIDI can be retrofitted at a price [see MIDI Retrofits].

Part of the reason for the Chroma's fearsome programming reputation is the fundamental freedom you are offered in terms of signal flow, namely, that you can choose from some 16 basic routing configurations to start with.

The level of flexibility runs through most of the modules: The oscillators can choose from a 1-63 value mix of sawtooth variable pulse waveforms and the filters are switchable between highpass and lowpass; there are 16 modulation sources for oscillator modulation, 16 LFO waveforms... This can be daunting enough at the best of times, but the Chroma makes it worse by failing to name individual parameters on its control panel. Two rows of pressure-sensitive pads double as patch select and parameter select switches, and you must either simply remember that pad number 13, say, governs envelope amount based on key velocity or glue the parameter table to the top of the instrument. The display merely shows numbers.

Idiosyncratic though it is, the Chroma, nonetheless, found many friends in the upper echelons of keyboard life during the early 1980s, most prominently Peter-John Vettesse, who used the instrument extensively during his high-profile stint with Jethro Tull. The Chroma was a newsworthy axe to be seen with due to its sexy link with Apple computers (one of the first planned marriages of computer and keyboard), which spawned dedicated Chroma software for sequencing and patch librarian duties. The Interface Kit opened the door to 16-track sequencing with punch-in/out recording and selective track quantizing--pretty sophisticated for the time. A PC package was also produced. The Chroma was also a bit of a trailblazer in that a keyboardless "expander was produced (the Chroma Expander), again long before MIDI popularized the whole notion of expanders and modules.

Creditably, the regular keyboarded version makes a very decent stab at keyboard dynamics, a feature that was not high on, or possibly not even on, most designers' lists at the time. The action on this quirky 64-note keyboard is pleasantly weighted and, with some 256 velocity levels, sensitive.

Though we have much to thank the Chroma for in terms of computer-aided performance and velocity (the inclusion of velocity levels within MIDI is often credited to Dodds' perseverance on the matter), the Chroma's relevance in the mid-1990s is a little limited. If you can find one that has been programmed by a long-term (and therefore, hopefully, skilled) programmer, it'll turn up a few surprises, and the model still on active duty at Britain's Museum of Synthesizer Technology is a joy.

ARP and Rhodes are no longer in business.

The Fax
Keyboard: 64-note
Programs: 50
External storage: Cassette interface, 100 programs
Polyphony: 16-voice
Oscillators per voice: 2
Effects: 3-band EQ
Connections: 4 mono audio, two XLR, MIDI [with retrofit]
Dimensions: 1000 mm x 576mm x 144mm
Weight: 32kg
The Figures
Chief designer: Philip Dodds
Production run: 1982-1983
Approx. units sold: 3000
Options: Computer Interface Kit Model 1611
Sounds: None commercially available
Miscellaneous: Designer Philip Dodds appeared as a musician in the movie Close Encounters of the Third Kind, playing a giant ARP 2500
Orig. price (1982): $5295 (£3800)
Price in 1996: $750 (£2000)