Casio CT-840

lo-fi wavetable keyboard with ROM-Pack & key lighting

This keyboard has the same sound generator like Casio MA-130, but additionally a key lighting feature ("melody guide") with music stored on ROM-Pack cartridges. The CT-840 was apparently Casio's last big keyboard with the ROM-Pack feature.

Like MA-130, the CT-840 has the same great 100 lo-fi wavetable sounds and rhythms, but instead of the "poly/ texture" button it has a "tone mix" (dual voice) button to layer any 2 preset sounds. Additionally there are 5 responsive rubber drumpad buttons (switchable to 5 effect sounds) and a feature called "DO. RE. MI. Guide", which sings the main voice in a low resolution sample child voice (only monophonic). Important to mention is that despite many false claims this function has absolutely nothing to do with the sing input features found on Casio VA-10; the microphone jack of the CT-840 is only sent through the analogue amplifier and has no means of digital sound control or sampling.

Unlike with modern key lighting keyboards, not the keys itself but a row of tiny LEDs above the keys flash up to teach keyboard playing, but here the LEDs are placed like musical notes on note lines to show which key belongs to which note. In opposite to earlier ROM-Pack keyboards it has not only a melody guide, but also a chord training feature, that teaches to play fingered chords.

main features:

49 fullsize keys
built-in speaker
main voice polyphony up to 8 notes (only 7 with rhythm, 4 with accompaniment, "tone mix" halves polyphony)
100 preset sounds (same like Casio MA-130)
100 preset rhythms (same like Casio MA-130)
cipher buttons {"0".."9"} to select preset sounds & rhythms
volume slider (5 steps)
accompaniment volume slider (with rhythm, 4 steps, steals bit resolution)
"tone mix" button (layers any 2 preset sounds)
single finger & fingered accompaniment (only standard chords, manual organ chord with rhythm off)
fill-in button
tempo +/- buttons (44 steps, 40..256 BPM)
5 rubber drumpad buttons {phone bell, "laser beam" (sound 3), bird tweet, siren 1, siren 2 | base, low synth tom, high synth tom, snare, cymbal}
"DO. RE. MI. Guide" button (sings monophonic main voice notes {"do"," re", "mi", "fa", "so", "la", "si", "do"})
metronome button (replaces rhythm with high & low clave hits)
LCD display (shows actual chord, preset sound & rhythm number, but no tempo)
wavetable sound generator with sounds based 2 mixed low- res loop samples with independent, partly very complex algorithmic volume and pitch envelopes (like with Casio SA series).
CPU= "OKI M6567-04, 1915, Japan" (80 pin SMD)
chord sequencer (stores 100 chords, but no persistent memory).
"melody guide" keyboard play training feature (4 modes) with key lighting (44 red & green LEDs above the keys)
ROM- Pack music cartridge slot for key lighting and "auto play" (jukebox mode)
5 demo melodies (also used for key lighting)

DO-RE-MI
Twinkle Twinkle Little Star
Rudolph, the Red- Nosed Reindeer
When the Saints Go Marching In
Ach Du Lieber Augustin

auto power- off (erases chord sequencer data)
jacks for AC- adapter, microphone & headphone

notes:

A bit strange is that there is an unused section with empty holes on the amp PCB; possibly originally a different microphone amplifier was planned here and then left blank to circumvent a PCB design flaw; the given mike amp seems to be mounted on a small daughterboard instead. The rastered volume control is annoying, since the lowest volume is often too quiet, while the 2nd is already too loud. Annoying is also that the LCD can not display the actual tempo setting and that there are no separate volume controls for rhythm and accompaniment. The given accompaniment volume slider has only 3 volume steps and off, and it responds a little slow. Most interesting is for me that this instrument can play ROM- Pack cartridge music through its 100 ToneBank PCM sound engine, although the semi- analogue Casio MT-800 sounds much warmer and nicer here. Due to the ROM- Pack standard is older than the 100 ToneBank technology, ROM- Pack musics itself still can select only from each 12 particular preset sounds and rhythms. Strange is that these 12 preset rhythms are marked with an asterisk in the rhythm list on the control panel, while the 12 preset sounds have none.

The sound of this instrument is almost identical with Casio MA-130 (see there) but instead of the "poly/ texture" button there is a "tone mix" button to layer any 2 preset sounds, since the tone generator apparently has doubled internal polyphony. Also the "piano" sound may have a higher resolution.

The "DO. RE. MI. Guide" button replaces the melody voice (also with demos etc.) with a monophonic Japanese child voice that sings the note names {"do"," re", "mi", "fa", "so", "la", "si", "do"}. Unlike MC-32, this one sings the correct pitch in the whole melody section of the keyboard and only repeats a higher octave in the below it. Also sharps (black keys) are sung, although as note names of the corresponding flats. The voice sings quite Engrish "le" instead of "re". The sung note is played only about 1 second long, but is truncated with even shorter note. I am not sure if this bombastically advertised hype feature really helps much with learning notes; at least the low resolution sample quality of the voice is very noisy and thus makes a nice sound effect; unfortunately it can play only monophonic.

The rhythm and accompaniment is also very similar like MA-130 (grainy lo-fi samples) with the only difference that here there is also a manual chord mode (pipe organ timbre) with rhythm off. Unfortunately it plays nothing else than standard establishment chords and stubbornly ignores any other key presses even in fingered chord mode. When new keys are pressed in the chord section, it always stops the organ chord tone for a fraction of a second, even when the new key combination continues with the same chord. (This can be also used as a sound effect.)

The 5 drumpads are very responsive and play 5 sound effects after power-on. The "phone bell" rings like a mechanical one so long the pad is held. The "laser beam" corresponds to the 3rd keyboard section of the same preset sound. The "bird tweet" is a high short synth whistle with falling pitch, the "siren 1" resembles a synth tom with falling pitch, while "siren 2" howls up with strong and fast vibrato. (Names were chosen by me since the control panel only shows icons.) The "metronome" button replaces the current rhythm with a metronome made from low and high clicking clave sounds (high for first beat of a bar, low for the others), which makes also a nice alternative rhythm, since it can be combined with the given accompaniments and switch back and forward during running accompaniment.

The chord sequencer is fairly complex but has no permanent memory and thus looses its data by power- off and even by auto power- off.

The "melody guide" key lighting feature can use as well the 5 built-in demo musics as external ROM- Pack cartridges, and you can even play their music with any of the 100 preset sounds & rhythms by switching them in between (although the programmed music may switch them back). The built-in musics are selected when no cartridge is inserted. The song "DO-RE-MI" always starts with "DO. RE. MI. Guide" enabled, thus singing its notes. Beside the melody voice, you can also train fingered chord play with this instrument, a feature that was likely first introduced with the Casio MT-820 and MT-88.

A midsize keyboard with same features like Casio CT-840 but no key lighting and a built-in 15 song bank instead of the ROM-Pack slot was the Casio MA-220 (seen on eBay). Smaller 100 ToneBank instruments with ROM- Pack slot and 5 drumpads were the mini keyboard Casio PT-88 and its midsize variant PT-380. The oldest (and most noble sounding) ROM-Pack keyboard was the Casio MT-800.

*removal of these screws voids warranty...*

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