(photo from eBay, showing my specimen)
The sequencer can be also programmed by live play and then stepwise edited by hand (forward and backward), but it is not possible to store any instrumentation or rhythm changes, nor to playback plain "organ" chords without rhythm from it; besides notes and chords the sequences can only store 2 loop points for refrains and their repeat points - that's all. Entering sequences with chords is very awkward, because chords are entered and edited only stepwise in a different mode, in which the main voice stays muted and only the current note number is displayed on the LCD. I read that some people found also the barcode pen very awkward and difficult to use, but I had no problems with it; with some training it is easy to scan in an entire page within 10s. When a line is scanned wrongly, a drum sound indicates this, and on the LCD you can read which line needs to be re- scanned. Important is only to hold the pen a little tilted, and because it contains no own light source, it may need proper ambient light to work.
All main voice sounds consist each of 2 mixed digital sine(?) waves with different volume envelopes. This sound generator was apparently optimized to simulate organ and flute tones, because everything else sounds very unnatural on it; the timbres are quite hollow, a bit harsh and bass notes tend to turn very dull. Likely it was intended as a direct competitor to the digital waveforms of the Yamaha PC-100 and should proudly demonstrate the end of the squarewave era, but since it sounds quite thin (very dull bass), it was certainly no great success and thus later Casio keyboards (e.g. the great CT-410V) returned to squarewave based timbres. The MT-70 has only one fixed organ timbre for chords and also its analogue percussion sounds rather thin, thus all together the MT-70 sounds quite plain home- organ- like, and this not necessarily in a positive way. But at least it features an unusual arpeggio and some unusual main voice sounds those (by my knowledge) do not exist on any other Casio midsize keyboard.
In opposite to many other early Casio keyboards, the case of this one is not white but light grey. The original German retail price in a GermanConrad catalogue from 1986 was 799DM (about 400€).
notes:The quite complex analogue hardware of this instrument resembles much the Casio MT-60 and also somewhat the Casio CT-410V, but unlike these, in the MT-70 the timbres are not squarewave based but sound rather like slightly rough digital sine waves, and also the CPU (D7802G) outputs no sounds by itself but delegates this task to 2 identical soundchips (HD43517), those drive each a resistor array as a (10 bit?) DAC. The 1st soundchip outputs the main voice, the 2nd the chords, but in spite of the separate soundchips the instrument always reduces the main voice polyphony from 8 to 4 notes in chord mode, thus I can only imagine that by a design flaw the keyboard matrix decoder in the CPU contains too little memory to handle more than 8 simultaneously held down keys, which makes it cut down the polyphony. (For further technical details about this hardware family also see here.)The main PCB is vertically divided into 2 halves those are interconnected with ribbon cables. The left PCB contains apparently no digital components at all, but only the analogue percussion with 3 trimmer pots for snare, base and woodblock decay. On the LCD daughter board are 2 small ICs "MN12528, 37" (28 narrow pins) and "TC50H001" (16 pins). (I haven't analysed this instrument further yet.)
Interesting for playing is that the 10 semi- OBS sound preset buttons can be also rapidly pressed while keys are held down, which switches the sound or retriggers the envelope of the already selected sound without any noticeable delay, thus by rhythmically pressing these buttons many arpeggiator- like timbre changes can be created, though this button field can be regarded as a realtime sound control. (OBS sound buttons on most other Casio keyboards respond rather slow.) The left half of the LCD always shows a picture of the sound preset button layout, and black squares in it indicate the currently selected button + "select" button status. (Apparently Casio intended here to simulate the intuitive visibility of locking switches with non- locking ones, but in reality theses tiny black squares far away from the corresponding buttons are rather confusing; a set of LEDs directly at these buttons (like done with the sequencer controls) would have been moreinstructive. Later Casio (like with CT-410V ) also returned to locking push buttons instead.)
On the MT-70 only flute and organ presets sound fairly realistic, and even these resembles rather undistorted Hammond organ timbres. The "piano" consists of something like a plain sine wave with decay envelope, thus it features the likely dullest bass range ever heard on a so-called piano; possibly it should imitate an e-piano, but it resembles rather a dull Hammond organ bass with envelope, thus it is no wonder that after power- on the MT-70 selects the "pipe organ" as default sound instead. The "tibia" and "full tibias" are also organ (pipe?) timbres. The "celesta" resembles a music box, and its bass range rather a steel drum. Both "jazz organ" sounds are the same dull Hammond timbres, while the 2nd one begins with a more percussive key click. Also the "wood wind" sound resembles a Hammond timbre with a dull percussive click. The "chorus" is also just a plain pipe organ timbre, which perhaps may resemble a "vox humana" pipe organ rank, but has only very vague similarity with a human chorus. Otherwise the "synth brass" on the same button indeed sounds quite much like a synthesized human "wah" voice (although particularly the bass range is extremely hollow and resonant). The "wah brass" instead is no human voice nor anything brass- like, but yet another Hammond organ timbre; unfortunately it starts with a dull percussive click that sounds wrong particularly during polyphonic play. Likely Casio confused some sound names here when they designed the front panel. The "cosmic flute" is an electronic organ tone that starts with a percussive click (like a xylophone) and crossfades from a high to a medium octave sine wave. The "funky" sound resembles very much a steel drum and consists of a medium octave note rapidly followed by a high octave note with each a decay envelope. (You get almost the same sound by selecting the "piano" and then playing a 1 octave higher note rapidly followed by a 2 octave higher one. Interesting is that this sound has (by my knowledge) absolutely no relation to funk music, and that on other (later?) (e.g. CT-410V or MT-60) Casio keyboards instead different sounds with the names "funny" and "funny fuzz" were released, those all may have been the result of a successles attempts to program a "funky" e-bass sound, although none of these sounds like one. The "banjo" sounds rather hollow and resonant; the "xylophone" is a much duller version of it and sounds unnatural. The "vibraphone" is otherwise one of the more realistic timbres. The "synth bells" plays within 0.5s 3 notes (octave 0, octave +2, octave +1) on a sine wave timbre with decay envelope, thus it resembles a short arpeggio fragment. The "chime" is a brightly clanging metallic sound; high notes resemble a triangle, but the bass range sounds rather like telephone touch tones. This sound consists of 2 partial tones with 5 notes distance those have the same percussive decay envelope, and like "synth bells" it is great for new age music. When sustain is switched off, all sounds stop almost immediately after releasing the key, and the sound presets itself also contain neither vibrato nor tremolo.
The same sound engine like the MT-70, but with far more variations has also the early digital synthesizer Casiotone 1000p, on which the envelope and 2 timbre components for the individual sounds can be selected from each 10 variations (i.e. 1000 sound variations). The sine wave sound engine was apparently also employed in the ancient fullsize wood case keyboard Casiotone 701, but I only asked by e-mail about the sound preset names and couldn't listen to these yet to confirm this.
The accompaniment is similar flexible playable like the Testron one, and thus also accepts any disharmonic note combinations and not just those few ones that establishment has defined as "chords". But unlike later Casio keyboards (e.g. CT-410V or MT-60), the MT-70 features only a single fixed timbre (an organ tone with some sustain) for chords and accompaniment, thus also when played without rhythm, the rhythm switch can not be used here to select the chord section timbre. The arpeggio of the MT-70 behaves quite unusual, because when in fingered chord mode only one key is pressed in the chord section, the instrument plays the arpeggio track not continuously like other keyboards do, but fades it in and out and thus chops the chinking arpeggio note stream into separate bursts of notes (like if someone would slowly turn an imaginary arpeggio volume knob up and down again, synchronized with the rhythm bar speed). Only when more than 1 key is held down, the arpeggio plays continuously; the only other keyboard I know with this behaviour is my Casiotone 1000p, on which the arpeggio pattern can be even programmed by hand. With the MT-70 I also miss independent volume control knobs for the individual accompaniment voices.
My MT-70 came with a musical lesson book containing a stack of barcode score sheets for these 14 songs. In the ancient home computer magazine "Your Spectrum" (Issue 4, June 1984) was an article about connecting a Sinclair ZX Spectrum home computer with the barcode reader input of aCasio VL-5. This article contains a BASIC program and many technical details about the data format of the Casio barcode song books, and it says that the same program works also with the MT-70. The article can be found here.
Another instrument with LCD and sequencer was the Casiotone 7000 (seen on eBay) which had a large beige metal case with 61 fullsize keys, 12 rhythms (6+1 locking buttons) and programmable stereo chorus effects. Like the MT-70 it had an LCD display and 20 semi- OBS sounds selected through non- locking buttons, but it had no key lighting and employed a complex sequencer that could save its data on audio cassettes. But according to the rhythm names and most preset sound names it seems to be rather based on the Casio CT-410V hardware class. http://weltenschule.de/TableHooters/Casio_MT-70.html
Click here to listen to the MT 70, Mp3
It has a built-in drum machine,
Thanks to information on homepage.mac.com/synth_seal/html/casiotone1000pc.html