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RMI Keyboard Computer KCII

Dave Crombie tinkles the RMI Keyboard Computer — not so much a synth, more a souped-up organ.

To many, RMI is a name from the past, bringing back memories of the trusty Electrapiano, but RMI have not in fact let the grass grow under their feet. They have taken advantage of recent electronic developments and come up with a revolutionary musical instrument.

RMI, or to give their full name, Rocky Mount Instruments, is a subsidiary of the Allen Organ Company of America, who have themselves clocked up a few firsts over the years. Back in 1939 Allen Organs installed the first electronic church organ. 20 years later they were to develop the first commercial transistorised organ, and in 1971 they produced the first digital church organ. The Allen Organ Company is quite a large-scale business (they are quoted on Wall Street, and have several plants across America). Their main product has always been church organs, so with the advent of popular electric music Allen Organs turned one of their plants, Rocky Mount, over to manufacturing instruments for this market. Thus RMI was born.

The Keyboard Computer concept was originated in the Allen Organ Computer range, and the RMI Keyboard Computer (KC-II) takes a large number of the organ computer's basic features and incorporates them in a portable one manual instrument.

The proper definition of the KC-II is a polyphonic synthesiser, but it does not employ the usual analogue devices (ie voltage controlled oscillators, filters, and amplifiers) that have almost become synonymous with synthesisers. Instead of modifying several oscillator waveshapes the KC-II system constructs individual waveforms from scratch using digital electronic circuitry. For the technically minded, the KC-II can be described as a 'time-division-multiplexed parallel-processor', but more of that later.

The KC-II basically consists of a single manual 5-octave (C to C) keyboard, five groups of switches (presets, generals, Division A, Division B, and Division C), and a computer card reader, all housed in a high-impact moulded case with locking cover (height 9¾in, width 44in, depth 24½in) and weighs 99lbs. Folded up underneath the case are the legs, which are both sturdy and easy to set up. There is also a pedal assembly consisting of five pedal controllers (vibrato, channel 1, channel 2, attack/decay, and pitch bend) and three foot switches (latch, staccato, percussion/sustain).

Let us first look at the five groups of switches. Directly above the keyboard there is a bank of twelve switches which are the presets. These are: Strings, Electric Organ, Organ and Bells, Organ and Guitar, Horn, Electric Piano, Clav, Jazz Flute and Clav, Alto Recorder and Harpsichord, Bells, Pipe Organ, and Echo. To the left of the presets are six further switches, known as the generals, which consist of Chorus/vibrato, Transpose 16' or 8', Attack/Decay-short or long, Attack/Decay-Fixed or Variable, Footswitch-Sustain or Percussion, and Add Manual. The presets can be modified using the generals and foot pedals, but only one preset can be operated at a time, the priority being to the right. The instrument has two independent high impedance outputs both of which are activated by the presets enabling various stereo effects when used in conjunction with the pedals.

To describe all the presets in detail would take up the remainder of this magazine so I will concentrate on just a few to illustrate the versatility of the instrument, starting with the strings. These should be played in conjunction with the Chorus/Vibrato depth pedal, the two channel volume pedals, and the Attack/Decay pedal. (With practice you can manage without having four feet). If you use just one channel you get a single violin string sound. The Chorus/Vibrato pedal is used for phrasing (not phasing) and the attack/decay pedal is used as necessary, depending on the nature of the music. The keyboard is scaled to give a much faster attack at the top end than at the lower end, simulating the common property of acoustic instruments viz: higher pitched notes are faster and lower notes slower due to the physical size and resonance of the instrument (eg cello and violin). All this may sound a bit involved to obtain a string sound, but then a string section is a complicated sound generator and the string sound of the KC-II is in my opinion the best around (even better than the acclaimed Polymoog strings). The digital envelope generator adds to the string sound giving a 'bowing' effect to each note: this will be explained in more detail later. In addition, the staccato foot switch can be activated to give a plucking sound to the strings.

Another preset, the 'electric organ', convincingly recreates the electromechanical organ sound with third-harmonic percussion and two-speed revolving speakers. The 'Organ and Bells' preset is similar to the 'Electric Organ' except that there are bells on top. By cutting down the decay of the bells, they can be used as the percussion to the organ, a very nice sound indeed. The 'Jazz Flute and Clav' preset puts the Clav on one channel and the jazz flute on the other. The 'Jazz Flute' is remarkably realistic and even contains the characteristic overblow transients. The 'Bells' preset is also very good, using very complex waveforms to achieve the rich clanging sound, and the 'Pipe Organ' preset again is very impressive, creating a beautiful sound. You can even hear the air blowing through the pipes. Finally there is the 'Echo' preset. A strange one this, it repeats notes played but in a different tone colour one octave lower, the rate being controlled by the attack/decay.

The presets alone make up what would be a formidable musical instrument. However there are in addition three banks of switches above the presets. These switches operate the various waveshapes and modifiers which can be added to the presets or used to build up particular sounds. These switches are divided into three divisions (A, B and C) for purposes of stereo channelling and voice assignment, and are brought into action by the Add Manual switch. Division A consists of nine voices all assigned to channel one. Division B consists of six voices and five switches for chorus, envelope, and routing. Division C consists of seven voices and six switches for chorus etc. In addition to these voices the KC-II has an alterable waveform memory. An optical reader accepts tone cards containing data of waveforms which can be programmed into divisions B and C. A total of four tone card waveforms can be memorised at any one time. Once programmed, the additional waveforms behave just like the permanent waveforms. The KC-II comes with 15 tone cards, but in addition RMI/Allen have developed a library of over 150 cards which are obtainable at around £2 each. These cards are categorized into various groups: Mellow Ensemble, Strings, Brilliant Reeds-Percussion, Solo Flutes, Organ-Pipe and Electronic, Vowel-Human Voice, Harmonics-Percussion, Bells, Pulse Waves-Geometric. It must be remembered that these cards only contain waveforms, not the envelopes of the notes.

There is a useful effect available when using the latch button on the pedal board. This will, when activated, retain the chord held indefinitely. If another chord is then fingered it will not play immediately, but if, however, the latch button is released the new chord will sound, even if it has been released. By pressing the latch button quickly again the new chord can be latched in and a further chord programmed in for the next change. By using this method a solo on another keyboard can be played and chords that have been programmed at convenient moments can be changed just by activating the latch footswitch.

Internally the KC-II consists of twelve digital voice generators enabling up to twelve notes to be played simultaneously. Some of the more complex sounds are accomplished by having multiple voices on a single key. The KC-II uses its twelve generators in several modes:

1. They can all be assigned to one division for one sound per key.

2. They can be divided into two divisions for two sounds per key giving up to a six note chord.

3. They can be divided into three divisions for three different sounds per key giving up to four notes at a time.

The more complex presets, eg 'Bells' and 'Organ and Bells' fall into the third group, and accordingly these presets are 4-voice polyphonic. The 'Electric Organ' preset is six note polyphonic (one division giving the percussion only). It does not take long to get to grips with the limitations of each preset.

The envelope of each generator is digitally controlled, the attack and decay ramps being made up of staircase waveforms as opposed to the usual smooth ramp. This staircase waveform only becomes noticeable for very long periods of attack and decay, but it is this waveform that gives the string preset its remarkable bowing sound as mentioned earlier.

This instrument is beautifully laid out and is very easy to play. The keyboard has a very pleasing action and can be adjusted internally to suit personal taste. Changing sounds is straightforward with hardly any knobs to worry about, just switches. The card reader is also simple to use — it's almost impossible to feed in the card incorrectly. The footpedals are cleverly designed so that with a bit of practice two pedals can be operated with one foot. The pitch bend pedal bends up to a perfect fourth when the transposition switch is in the 16' position, and down a fourth in the 8' position, and has a powerful spring return mechanism. I feel it would have been useful to have been able to bend either up or down in both the 16' and 8' transposition positions.

There seems to me to be one tonal area in which the KC-II was lacking — that of recreating the sound of an acoustic piano (which I appreciate is difficult to synthesise electronically). I tried for some time to obtain a good piano sound, but with disappointing results. The only other criticisms I had with the instrument were that a couple of the switches seemed to be slightly faulty and that a small amount of mains modulation was apparent during pitch bending. But these faults, I feel, were peculiar to the particular instrument I reviewed.

The amplification used for the test was the recommended RMI 360 audio system which consisted of two 360 amplifiers and two G180 cabinets giving a very flat response. The cabinets use a 15in JBL speaker, with two tweeters and two midrange units. The amplifier delivers 110 watts into 8ohms and has a very wide sensitivity range virtually eliminating input clipping. The KC-II demands very good quality amplification; this system seems to provide it.

RMI have gone to a lot of trouble to produce and present a good product. The owner's manual is really excellent, consisting of around 150 pages, including every last detail of the instrument and how to get the best out of it, as well as a set of 'patch diagrams' for simulating many other instruments, eg sax, vibes, steel drums, cathedral choir and bells. There is also an excellent 12in record obtainable which illustrates the sounds available far better than I can in this article. I suggest that anyone remotely interested in the instrument tries to get hold of a copy. Unlike some demonstration records, the recording isn't touched up with studio effects.

When one thinks of a computer generating musical tones one might imagine that the sound produced would be sterile and clinical. The KC-II has managed to overcome this problem and has a very natural sound, even incorporating the imperfections that make musical instruments musical. It is not cheap, but seems a reasonable price for a keyboard that gives realistic imitations of a wide range of musical instruments, as well as many original and beautiful sounds of its own. If this is what you want, this is the one for you.

rrp £3250/$4750

Dave Crombie is resident electronic design engineer at Rod Argent's professional keyboard store in Central London.

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Sound International - Jun 1978

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Review by Dave Crombie

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