Casio MT 45

 (pretty analogue keyboard with arpeggio accompaniment)
This beautiful white Casio keyboard has wonderful warm analogue sounds, arpeggio accompaniment and the same unique, dark and sonorously droning squarewave bass tones like the "organ" sound of the Hing-Hon EK-001.


Despite its age, the control panel design with its blue lines, pastel coloured softline shaped knobs and switches looks still noble and modern and resembles a bit the "Aqua" user interface theme of Apple Macintosh computers. This instrument was also released as Casio MT-46 with red and less pretty control panel ornaments.

main features:

• 49 midsize keys
• 8 note polyphony (but left keyboard section stays always in manual bass/ chord mode, thus only 31 keys usable for main voice)
• 4 note polyphony in chord section
• separate knobs for main and rhythm + accompaniment volume
• tempo knob
• 8 preset rhythms {pops, disco, 16beat, swing | samba, beguine, tango, waltz} selected by a 4-step slider + switch
• 8 preset sounds {piano, elec. piano, organ, pipe organ | harp, accordion, clarinet, violin} selected by a 4-step slider + switch
• mode switch {manual bass, fingered, casio chord}
• switch for 2 bass timbres (squarewave based)
• arpeggio switch
• chord memory switch (chords stay held after releasing key when on)
• rhythm fill-in and synchro button
• vibrato and sustain switch
• main voice CPU "HD44140, 3A 43" (56 pin SMD) with timbres based on multipulse squarewave tones with different digital envelopes, those are differently low pass filtered through capacitors. It makes very warm and pleasant timbres, but envelope release phase is truncated too soon, which makes piano- like tones less natural.
• accompaniment CPU "NEC D930G  011, 8434XK" (80 pin SMD) which produces different multipulse squarewave tones (partly with capacitor envelope) and trigger pulses for external analogue drums. (For technical details about this chip see CT-410V.)
• analogue percussion {base, snare, open cymbal, close cymbal, woodblock} which apparently uses no transistor noise. The cymbal timbre sounds half- way metallic and resembles the one of Yamaha PS-2, thus it may be mixed from 2 shift register feedback noises.
• headphone and cinch output jacks

Note the elegant control panel design.

eastereggs:

This instrument employs the same very versatile accompaniment CPU like the Casio CT-410V, thus there are lots of keyboard matrix eastereggs available.  (For technical details see there)

 4 additional rhythms (rock, latin swing, bossa nova, slow rock)

 2 additional bass variations (III, IV)

 3 additional accompaniment variations (II, III, IV)

 3 additional arpeggio variations (II, III, IV)

 6 additional main voice keys

On the PCB with the sound output jack are empty component holes for an additional jack (volume pedal?). I didn't upgrade my MT-45 because I already own the CT-410V, which had most of these features and I enabled all the hidden ones.

notes:

I bought this instrument in very dirty state, and during transport(?) the plastic tab/ hook under one key cracked off from accidentally bending it too far upward. (I replaced the tab with a piece of insulated copper wire and hotglue.) Someone had written the key names above the keys with blue Edding; my attempt to remove them with isopropanol also damaged the blue and black stripe pattern printed on the case there. Unusual with this keyboard is, that the keys are made from separate plastic parts and not hanging on one common, bendable plastic strip; thus I assume that it must be very old. The silicone contacts below are also separate parts and were stained with dirt and a sticky stuff (likely adhesive tape glue from the felt strip above); although I cleaned all these parts thoroughly, the keys still don't respond perfectly yet.The electronics of the MT-45 employs the same very versatile D930G accompaniment CPU like the Casio CT-410V (and many other Casio instruments), although here only few features of it are used. Unlike in many other Casio keyboards, it is here also not combined with the versatile D931C main voice soundchip (that was dedicated for it?), but a foreign main voice CPU "HD44140" (same like in the rhythmless Casio MT-11?) with only 8 preset sounds is used instead. Unlike the D931C, the HD44140 does not communicate at all with the D930G, but uses a completely independent keyboard matrix for all main voice related keys and switches. (Possibly Casio had not finished the D931C yet when the MT-45 went in production.) Unfortunately this results in that the accompaniment section at the left half of the keyboard can not be switched off, thus these keys can not be used for main voice play when neither chords nor manual bass is wanted. The only benefit from this is that the polyphony is not reduced by accompaniment.
This instrument plays high quality analogue timbres, those although not always natural, reproduce a warm and very pleasant sound; it does not sound typically C64- like thin, but resembles rather full- size home organs of that era. Like with Casio VL-1, the release phase of main voice envelopes seems to be linear and thus sounds unrealistic since it fades silent too soon with an audible end click. When sustain is switched off, all sounds stop almost immediately after releasing the key. When sustain is on, sounds with decay envelope (piano, elec. piano, harp) ignore the key press duration and sound always with a fixed duration instead. The "elec. piano" sounds like a banjo, and also the normal piano resembles more a picked string. The "harp" and "organ" sounds seem to add a bit of analogue distortion (or a mixed suboscillator with very short independent envelope??) during attack phase.
The accompaniment is almost as flexible playable like the Testron one, and thus also accepts any disharmonic note combinations and not just those few ones that establishment has defined to be "chords". The available styles on the MT-45 correspond to chord variation "I", bass variations "I" & "II" and the default arpeggio (= variation "I"?) of my CT-410V. The percussion of the MT-45 are analogue and resemble the CT-410V, although it has 2 drums less than the latter. Interesting is that the MT-45 produces a much softer, duller and more pressureful bass than the CT-410V, which timbre resembles a triangular wave or Roland TB303 (without resonance), while the CT-410V bass is a more sonorous droning ordinary squarewave tone. The MT-45 sounds also brighter than the initially quite muffled CT-410V, and generally I find its timbre somehow fresher and clearer and thus like it a bit better, despite the great CT-410V has far more capabilities. By sound and functions the Casio MT-45 instrument is mostly comparable with my Yamaha PS-2, but unlike the latter it is not that extremely compact and features more rhythms, sounds and nice sounding arpeggios. Even the internal speaker is of very reasonable quality. I only yearningly miss independent volume control knobs for the individual accompaniment voices (fortunately my CT-410V has them).

modifications:

• polarity protection diode added, power supply jack polarity corrected.

Despite the case shape and button layout of the MT-45 is identical with the (older?) Casio MT-60, the latter contains a much bigger PCB with totally different hardware, which features far more sound presets but thinner sounding accompaniment.