Casio PT-80

This keyboard has many similarities with the Casio VL-Tone 1 and PT-1, but includes a "melody guide" key lighting feature for music teaching (not the keys itself light up but a row of small LEDs above them) and a ROM- Pack music cartridge slot.

Casiotone 401

This was Casio's first keyboard with accompaniment and (so far I remember well) also the world first keyboard with automatic single finger accompaniment.

The Casiotone 401 has 16 unusual, partly incredible dry semi- analogue preset sounds and 16 analogue rhythms; also the bass sounds nicely warm and seems to be based on a triangular wave. Unusual is the "hold" switch, much like the manual fingered chord mode (with chord memory) on newer keyboards, here also the melody voice notes hold until any other chord or key combination is played. The noble designed case is unusually heavy, because it is made of plastic coated steel instead of genuine wood

Casio MT-18


(photo taken from eBay, showing my specimen)

 
This brown keyboard is simply the midsize version of Casio PT-80. Thus the main voice is still monophonic despite bigger keys. The specimen I bought even came with the same ROM-Pack RO-551.

different main features:

  • 32 midsize keys
  • better speaker (without disturbing resonance)
  • different CPU= "HD61703A01, 5B 33" (80 pin SMD)

notes:

Very unusual is that the MT-18 contains a different CPU despite the behaviour is identical with the PT-80. Thus I guess that the same CPU core was only re- released in a different package or manufacturing process for technical reasons, while the internal circuit stayed the same. Also the PCB layout and material looks very different. Despite it worked well, I found in my Casio MT-18 an exploded electrolytic capacitor (which I replaced).
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Casio PT-20

(photo from eBay, showing my specimen)

This tiny instrument seems to be just a downsized Casio PT-30 and sounds very similar. (I haven't examined the hardware yet.) Unlike the latter it is missing the LCD, the cartridge slot, some of the sequencer buttons, the transpose buttons and 2 high note keys (thus also the "arp. 6" rhythm). Instead of separate rhythm and chord volume sliders it has only a combined slider. Its small case resembles the Casio PT-1. The original German retail price in a German Conrad catalogue from 1986 was 199DM (about 100€).

The likely most advanced member of this hardware family was the ultra- rare keyboard boombox Casio KX-101 (37 mini keys, chord button pad, complex sequencer that saves data on audio cassettes), which was even 4 note polyphonic.