The Rhodes Chroma, initially the ARP Chroma, is a

polyphonic Polyphony ( ) is a type of musical texture consisting of two or more simultaneous lines of independent melody, as opposed to a musical texture with just one voice ( monophony) or a texture with one dominant melodic voice accompanied by chords ...

multitimbral Monotimbral (from the root prefix ''mono'' meaning one, and ''timbre'' meaning a specific tone of a sound independent of its pitch) is usually used in reference to electronic synthesizers which can produce a single timbre at a given pitch when pre ...

, microprocessor controlled,

subtractive synthesis Subtractive synthesis is a method of sound synthesis in which Harmonic_series_(music)#Partial.2C_harmonic.2C_fundamental.2C_inharmonicity.2C_and_overtone, overtones of an audio signal are attenuated by a audio filter, filter to alter the timbre of ...

analog synthesizer An analog synthesizer () is a synthesizer that uses Analogue electronics, analog circuits and analog signals to generate sound electronically. The earliest analog synthesizers in the 1920s and 1930s, such as the Trautonium, were built with a var ...

developed in 1979-1980 by ARP Instruments, Inc. just before the company's bankruptcy and collapse in 1981. The design was purchased by CBS Musical Instruments and put into production by their

Rhodes Rhodes (; ) is the largest of the Dodecanese islands of Greece and is their historical capital; it is the List of islands in the Mediterranean#By area, ninth largest island in the Mediterranean Sea. Administratively, the island forms a separ ...

Division in 1982 as the Rhodes Chroma, at a list price of US $5295. Rhodes also released a keyboard-less version of the Chroma called the Chroma Expander at a list price of US $3150. The Chroma was one of the early microprocessor-controlled

analog synthesizers An analog synthesizer () is a synthesizer that uses analog circuits and analog signals to generate sound electronically. The earliest analog synthesizers in the 1920s and 1930s, such as the Trautonium, were built with a variety of vacuum-tub ...

. It was designed before

MIDI Musical Instrument Digital Interface (; MIDI) is an American-Japanese technical standard that describes a communication protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, ...

and featured a 25-pin D-sub connector computer interface used to slave the Expander to the Chroma. Also, an

Apple IIe The Apple IIe (styled as Apple //e) is the third model in the Apple II series of personal computers produced by Apple Inc., Apple Computer. It was released in January 1983 as the successor to the Apple II Plus. The ''e'' in the name stands for ...

interface card and sequencing software was available. The Rhodes Chroma and Expander were discontinued in 1984. Somewhere between 1400 and 3000 Chromas and Expanders were built.

Keyboard velocity and pressure

The Chroma has a velocity-sensitive

keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Mus ...

consisting of 64 weighted, levered wooden keys that resemble piano keys. Every Chroma has software and interface hardware for an optional

pressure-sensitive

sensor, but few units have the original factory pressure sensor installed. In 2009 a pressure sensor retrofit kit was produced by a third party. At the time of writing (2015) the kit may still be available.

Polyphony

The Chroma has sixteen synthesizer "channels" each consisting of one oscillator,

waveshaper In electronic music, waveshaping is a type of distortion synthesis in which complex spectra are produced from simple tones by altering the shape of the waveforms. Uses Waveshapers are used mainly by electronic musicians to achieve an extr ...

, filter and amplifier. Sound programs can use one channel per voice to produce sixteen voice

polyphony Polyphony ( ) is a type of musical texture consisting of two or more simultaneous lines of independent melody, as opposed to a musical texture with just one voice ( monophony) or a texture with one dominant melodic voice accompanied by chord ...

. However, most sound programs use two channels per voice which delivers a fatter sound, but reduces the

to eight voices.

Architecture

The Chroma's sixteen synthesizer channels consist of one Voltage Controlled Oscillator, Waveshaper, Filter, and Amplifier under software control via multiplexed analog voltage control channels. The channels are grouped into eight pairs. One channel in each pair is labelled "A" and the other "B". Although the oscillators, filters and amplifiers themselves are voltage controlled, the overall control of the synthesizer channels is entirely in software. The embedded computer generates thirty-two

ADSR envelope In sound and music, an envelope describes how a sound changes over time. For example, a piano key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero. An envelope may relate to elements such ...

s (two per channel, one with delay) and sixteen LFO sweep signals in software. Signals from the levers, pedals, control panel or the keyboard are all encoded digitally, processed by the computer, and sent to the synthesizer channels on the voice cards via several multiplexed analog control lines and a number of digital control registers. Sound programs can use one channel per voice to produce sixteen-voice

. However, more synthesizer power is available when channels are paired together. This yields two oscillators, two waveshapers, two filters, two amplifiers, two glides, two LFO sweeps, and four ADR envelopes, in addition to the performance controls.

Modular configuration

The Chroma uses an Electronically Reconfigurable System which allows the VCOs, VCFs and VCAs to be reconfigured, or "patched" like

modular synthesizer Modular synthesizers are synthesizers composed of separate modules for different functions. The modules can be connected together by the user to create a patch. The outputs from the modules may include audio signals, analog control voltages, ...

s, but without the

patch cord A patch cable, patch cord or patch lead is an electrical or fiber-optic cable used to connect ("patch in") one electronic or optical device to another for signal routing. Devices of different types (e.g., a switch connected to a computer, o ...

s. Instead, the Chroma digitally stores all of the parameters which determine a sound. Sound programs can also be saved to and loaded from cassette. On page 4 of the Rhodes Chroma Programming Manual, they boast "The Chroma has better patching capabilities than most modular systems, and it's fully programmable." In fact, the Chroma is often compared to

s like the

ARP 2600 The ARP 2600 is a subtractive synthesizer first produced by ARP Instruments in 1971. History Developed by a design team headed by ARP namesake Alan R. Pearlman and engineer Dennis Colin, the ARP 2600 was introduced in 1971 as the successor to ...

. A Chroma sound program can be composed of two oscillators, filters and amplifiers in one of fifteen different configurations. Each configuration connects (or patches) the oscillators, filters and amplifiers together in different ways to provide for a wide variety of possible sounds. For example, filters can be arranged in series for 4 pole or band-pass response, or in parallel for notch filtering. In addition, some configurations feature oscillator synchronization, filter

frequency modulation Frequency modulation (FM) is a signal modulation technique used in electronic communication, originally for transmitting messages with a radio wave. In frequency modulation a carrier wave is varied in its instantaneous frequency in proporti ...

or ring modulation. When editing a sound program, the configuration is selected via parameter "Patch". The values range from 0 through 15.

Control panel

The Chroma control panel consists of 71

membrane switch A membrane switch is a custom switch assembly that can open or close the conducting path in an electrical circuit and requires at least one contact made of or attached to a flexible substrate. Its assembly differs from traditional mechanical switch ...

es. Most of them are multi-purpose and are used to select sound programs or sound program parameters, when in edit mode. A single slider is used to change parameter values. Competing synthesizer designs of the time, like the

Oberheim OB-8 The Oberheim OB-8 is a subtractive analog synthesizer launched by Oberheim in early 1983 and discontinued in 1985. As the fourth product in the OB-series of polyphonic compact synthesizers, the OB-8 was the successor to the OB-Xa. About 3,000 ...

, had dozens of knobs and mechanical switches (as opposed to

es) on their control panels. The Chroma's economical approach to control panel design was copied by many later synthesizers like the

Yamaha DX-7 The Yamaha DX7 is a synthesizer manufactured by Yamaha Corporation from 1983 to 1989. It was the first successful digital synthesizer and is one of the best-selling synthesizers in history, selling more than 200,000 units. In the early 1980s, th ...

. A unique feature of the Chroma is that, when you operate a membrane switch, a "tapper" bumps the underside of the control panel, so as to mimic the tactile feedback of operating a conventional mechanical switch. This is an early example of haptic feedback technology.

Power supply

Perhaps the worst feature of the ARP/Rhodes Chroma is the factory original power supply. It runs very hot, it is unreliable and it is very heavy. In 2008, a third party designed and produced a digital switching power supply replacement kit.

CPU

The main microprocessor in the Chroma and Expander is a 68B09, and it has a computer interface consisting of a 25-pin D-sub connector. The factory original Chroma CPU board has 2

AA batteries The AA battery (or double-A battery) is a standard size single cell cylindrical dry battery. ANSI and IEC battery nomenclature gives several designations for cells in this size, depending on cell features and chemistry. The IEC 60086 system c ...

to preserve memory while the power is off. Many Chroma CPU boards have been damaged from

battery leakage Battery leakage is the escape of chemicals, such as electrolytes, within an electric battery due to generation of pathways to the outside environment caused by factory or design defects, excessive gas generation, or physical damage to the battery ...

. In 2006, a third party designed and produced a Chroma CPU board replacement kit known as the CC+. The CC+ is available with optional native MIDI support.

External control and MIDI

The Chroma was designed and released before the introduction of

. The Chroma's main microprocessor was a 68B09 with a computer interface consisting of a 25-pin D-sub connector. An

interface card (used to connect to the Chroma's D-sub connector) and sequencing software was released by ARP and Fender Rhodes. Multiple third parties came out with Chroma-to-MIDI converter boxes. They use the 25-pin D-sub connector to interface with the Chroma.

Accessories

The Chroma came with the usual complement of accessories plus some unique extras. In addition to a single footswitch (dedicated to program changes) and a programmable variable (volume type) foot pedal, the Chroma came with a unique Dual Footswitch Assembly. The dual footswitch is a rugged, heavy, solid piece of hardware that mimics a pair of standard piano foot pedals with programmable functions including sostenuto. The Chroma also came with a custom designed, heavily padded, ATA Anvil (R) case with a pedal compartment. The rumor was that early units shipped without a case were damaged in shipping because the Chroma is so heavy and fragile (a fair criticism). In any case, the Chroma and Expander included a road case.

Chroma expander

Fender also released a keyboard-less version of the Chroma called the Chroma Expander. Like the Chroma, the main microprocessor in the Expander is a 68B09 with a computer interface consisting of a 25-pin D-sub connector. The Expander can be slaved to the Chroma via the 25-pin D-sub connector. Third party Chroma-to-MIDI converter boxes produced for the Chroma also work for the Expander.

References

External links

rhodeschroma.com - a site and community dedicated to the Rhodes Chroma

ARP Chroma announcement
* http://www.vintagesynth.com/misc/chroma.php
Rhodes Chroma Demo, Part 1

* https://www.facebook.com/RhodesChroma * ttp://www.synthmuseum.com/rhodes/rhochroma01.html Synthmuseum.com - Rhodes Chroma* ttp://www.redshift-consulting.com/enabler.html The ENABLER is a custom made 95-knob dedicated MIDI controller for the CC+ equipped Rhodes Chroma.
Synthtopia Rhodes Chroma

Rhodes Chroma (@rhodeschroma) - Twitter

Rhodes Chroma Editor for iPad by Matrix

Rhodes-ARP Chroma - Specifications, pictures, prices, links, reviews and ratings - Sonic State
* http://www.native-instruments.com/forum/threads/rhodes-chroma-ni-kontakt-sample-library.180159/
Rhodes Chroma Ni Kontakt sample library , NI Support Forum
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