Casiotone MT-800,
Casiotone MT-85
keyboard with key lighting, ROM-Pack & analogue rhythm

Casio MT-800

This was apparently Casio's first keyboard that uses music stored on ROM-Pack cartridges for key lighting feature ("melody guide"). According to a copyright date on the default cartridge, the instrument was likely designed in 1983. Unlike with modern such keyboards, not the keys itself but a row of tiny LEDs above the keys flash up to teach keyboard playing.
(pictures taken from eBay)

In opposite to its predecessor Casio MT-70, the sequencer of this instrument can be programmed by simultaneous live play of main voice and chords. Unfortunately it lacks any edit features which limits its use. Despite this instrument is based on the same chip set like the great Casio CT-410V, it has far less sound variations and even the accompaniment only accepts standard chords. In spite of this the semi- analogue sounds are of high quality and also the analogue percussion sounds are ok.

The original German retail price of the MT-800 in a German Conrad catalogue from 1986 was impressive 999DM (about 500€); a Casio MT-68 cost only the half. A fullsize key variant of the MT-800 was released as Casio CT-810. (It had a silver metallic case shaped like the CT-410V and 5 big knobs to the left of the ROM-Pack slot - despite same hardware, according to CasioNova site it cost in 1984 enormous 899$.)

main features:




The MT-800 contains a very complex analogue hardware with stacked large PCBs that resembles much the Casio CT-410V (for technical details and explanations see there); internal speakers likely would not have fit into the crowded case. But the small detachable stereo boxes sound quite nice and even have a reasonable amount of bass although they have only 1.6W. They can be either attached to the back of the instrument case or stand behind it. Unfortunately the only 30cm short speaker cables (with walkman style 3.5mm plugs) limit the placement a lot, and the sharp edged sheet metal stands can easily scratch the instrument case during transport. The same external speakers had also the Casio MT-410V, which is the small case version of the CT-410V. The amplifier produces quite noticeable static noise. A bit odd is that the MT-800 was intended for a 9V DC power supply, while all other small Casios employ 7.5V instead. (Possibly Casio feared that the power amplifier would make clipping distortion at high volume.)

The MT-800 also employs almost the same D931C/ D930G chip set for sound generation like the CT-410V and even has a stereo chorus (but no synthesizer filter). First I thought that in opposite to the latter not the accompaniment IC "D930G" acts as the main CPU (polls the keyboard matrix etc.) but that everything is controlled by an external CPU "HN61364P" that handles the sequencer/ ROM-Pack stuff and simulates key press events for the D930G or the like to control the sound indirectly. But now I am not sure anymore; likely the HN61364P is only an external ROM or RAM because it has only 28 pins and on the PCB of my Casio MT-85 it is labelled "µPD2364EC-074" and Casio chips with "D23..." are usually ROMs. Also the internal software version of the D930G seems to be different from the CT-410V; while the latter has a "D930G 011", here it is a "D930G 017". Fortunately the MT-800 lacks the annoying muffling capacitor of the CT-410V, which made all sounds very dull. On the PCBs are various trimmer pots; 5 of them control percussion decay speed. (I haven't analyzed the hardware closer yet.)

While the vibrato, reverb, envelope and octave select functions on other instruments were switched strictly by hand, the MT-800 uses only 12 well tweaked preset sounds those switch these features by themselves, which makes many presets sound much more natural than normal default presets on the Casio CT-410V (see there) despite they are still made from 2 mixed and filtered squarewaves. E.g. the "trumpet" sounds quite realistic now. The sounds "flute", "celesta", "violin", "synth. flute" are transposed 1 octave up. The "elec. guitar", "trumpet", "flute", "violin", "clarinet", "synth. flute" include a delayed vibrato. The "sustain" button seems to activate with many sounds rather the "reverb" effect of the D931C/ D930G chip set than the dedicated sustain effect. (I don't know if the CPU control over the D930G can be circumvented by modifications to regain full manual control over its many sound selection parameters like with the Casio MT-65/ MT-68 or my modified CT-410V.)

The stereo chorus adds a mixture of panning, vibrato and a little chorus to the main voice sound to simulate a rotary speaker; but unlike with the CT-410V, here it can be only switched on or off; it has no speed control and runs slowly with only about 2Hz, which makes of the vibrato a strange mild howl. The intensity of the chorus component seems to be also lower than on the latter, thus the vibrato and panning is most audible.

Unlike the great CT-410V and all my other analogue Casio MT keyboards, the accompaniment of the MT-800 is very restricted since it recognizes only 12 standard establishment chords consisting of each 3 or 4 notes; with any other note combinations it plays only the lowest note as bass (which repeats within 1 octave and thus makes no good manual bass). Despite the very versatile D930G sound chip, this stubborn accompaniment uses always the same plain electronic organ tone for bass and chords, and unlike the predecessor MT-70, it has no arpeggio. Also in organ chord mode (without rhythm) the timbre can not even be switched by pressing different rhythm buttons. The only improvement in comparison to the CT-410V hardware is that this accompaniment does not reduce the main voice polyphony from 8 to 4 notes; likely this was a limitation of the keyboard polling algorithm in the D930G, which is circumvented by the external CPU. The accompaniment always uses the stereo chorus, which gives especially the organ bass tone an interesting droning timbre (a bit like a propeller aeroplane). This analogue bass sounds soft and pressureful - a bit like a church organ.

The analogue percussion sounds much like on Casio CT-410V (see there), but the rhythms seem to be also controlled by the main CPU, because there are e.g. 2 different swing rhythms, those don't exist within the preset rhythm of the D930G chip. The new rhythm set was likely standardized for ROM-Pack instruments, because they all include the same rhythm names although their percussion sounds different.

The sequencer is less awkward than on Casio MT-70, but it can not be edited anymore and thus is of little use (only melody and chord track can be erased separately). Also the "one key play" buttons of the latter are gone; only a "one key chord" button permits to play recorded chords one by one. Generally the MT-800 appears despite its external stereo speakers far less professional than the MT-70, because it has not only less main voice sounds and no display, but permits way less user controllable variations of given presets and behaves in some ways similarly stubborn than Casio's later ToneBank instruments. Quite interesting is that this instrument loads any played songs from the ROM-Pack cartridge first into the internal sequencer RAM (takes about 3 seconds; smaller keyboards like the Casio PT-82 don't do this). Beside chord, rhythm and monophonic main voice, the ROM-Pack musics contain a 2nd monophonic melody voice (called "obligato" by Casio) which is apparently stored on an additional sequencer track. Unfortunately this track can not be recorded by hand (possibly a button can be added as an easteregg for this). ROM-Pack musics also contain instrumentation and rhythm changes, those can also not be recorded manually too. For play training, chord and melody track can be muted separately, but these buttons don't work while the sequence is playing. Great is that you can play (up to 4 note polyphonic!) while the sequencer is played back. The "obligato" voice volume can be only set together with the rest of the accompaniment; I badly miss a separate volume control for it because it tends to be too quiet.

The MT-800 seems to have been indeed the first ROM-Pack keyboard, because its behaviour has various glitches and is less elegant than later such instruments (e.g. Casio PT-80 and PT-82). These smaller instruments indicate e.g. with a walking light on the LED row above the keys that the user shall select a song number from the cartridge, and a click indicates that an empty number was selected, while a correct number starts that song. With the MT-800 instead there is only a static light above the key with the last selected song number, and during selection even the note of pressed keys still sound. (You can even play polyphonic on the keyboard in this mode, which was certainly not planned by Casio.) After selection you have to press "memory start" to load the song (possibly a safety measure because it overwrites the sequencer content). Selecting a non- existing song number or the rightmost key ("demo") selects the built-in demo song "Tanz der Stunden". On later instruments the rightmost key plays all songs on the cartridge in a sequence. Selecting instead of a melody number the keyboard key "F" (left next to the lowest number key) loads a lot of bizarre sounding (semi- random?) note mess into the sequencer. Other glitches include that after connection to supply voltage there is also mess in the sequencer and often the "sustain" or "stereo chorus" effects are active despite their locking buttons are not pressed (press them to fix this). But like with later ROM-Pack instruments already here 2 lights indicate the keys for the current and next played note (current = lit, next = flashing), and you can select the melody guide either to wait for the player (press "start" to begin) or to continue with its programmed tempo (press "memory start" to begin). You can also switch the LED row off by pressing "cancel" before starting the melody guide; thus basically all 4 melody guide levels of the Casio PT-82 (but not the "rating" feature) already exist on this early instrument. While a song plays from the ROM-Pack, you can even switch the rhythm off and do many other manual things those with later ROM-Pack instruments don't work anymore.

My Casio MT-800 came with the default ROM-Pack RO-201 "Fun With Your Casio Keyboard", which contains 15 songs. Unlike my other ROM-Packs it has a shiny sheet metal bottom instead of the usual black plastic one. It is quite strange that this old instrument was shipped with a 15 song cartridge, while later Casio keyboards came with ROM-Packs with each only 4 songs, despite the price of ROM capacity certainly didn't increase over the years. In the manual of this cartridge several other ROM-Packs are advertised with also each >10 songs. With my MT-800 I also got the ROM-Pack RO-253 "Pop/ Rock".

Predecessor of the MT-800 was the Casio MT-70 (with barcode pen instead of ROM cartridges). Successors were likely the MT-820 and MT-88 (both similar, with internal speakers). In eBay announces some people claimed that you could also save own musics from the sequencer onto the ROM-Pack "diskette", but I guess this was just a wrong description; I have tested to insert the RAM-Pack RA-1 of my PT-50 into the MT-85 (hardware like MT-800), but it gets simply ignored. The likely last non- toy Casio keyboard with ROM-Pack slot was the Casio CT-840.

Casio MT-85

This rare keyboard was basically a re- released  mono version of the wonderful Casio MT-800; it only lacks the 2nd speaker and stereo chorus and has a boring case style, but is otherwise technically identical.

In my German MT-85 manual there is even a typo somewhere that calls the keyboard "MT-800". The manual claims that it was packaged with the ROM-Pack RO-201 (like with MT-800) while my used specimen came with a RO-551. A brown MT-85 version was released as Casio MT-86 (seen on eBay).

different main features:




To simplify the complex MT-800 hardware and make the speaker fit into the case, Casio here integrated some of the discrete components (mainly analogue percussion?) into 3 black hybrid modules.
Thus unlike the MT-800 this keyboard contains no stacked daughter PCBs anymore but only 2 (still large) main PCBs. (Similar hybrid modules were used in Casio KX-101.) Interesting to mention is is that like with MT-800 and MT-85, Casio later also re-released their stereo ROM-Pack keyboard MT-820 as the mono version Casio MT-88, which was also only missing the stereo chorus and a 2nd speaker. Strange is that the accompaniment CPU of the MT-85 has the type number "D930G 018" ,while the MT-800 had a "D930G 017", thus it may contain a different software version despite the user interface behaviour of both instruments is identical. The IC "HN61364P" has the PCB label "µPD2364EC-074", which may be a relative of the "D23C64EC ..." ICs in Casio MT-500 and MT-520.
 removal of these screws voids warranty...    
back to tablehooters collection