From Keen On Keys.

The Casio MT-400V, released in 1984, is a small keyboard with 49 mid-sized keys, 8 note polyphony, 12 styles, 20 tones, vibrato, sustain/reverb and stereo chorus. It’s main feature is a filter control with ADS and LFO modulation. It uses the NEC D930/931 ICs which were used for many Casio keyboards between 1983 and 1986. There’s also a larger version existing, the CT-410V.

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Listen to some tracks on Soundcloud:

0:00 Intro
0:05 Overview
3:36 A Look Inside
7:44 Comparison with MT-65
9:12 Filter Control
11:42 ADS Envelope
14:31 Tone Examples
17:56 Envelope Triggering
20:11 LFO Modulation
21:49 Chord Mode
22:46 Rhythm Examples
25:02 Bass/Chord Examples
28:33 Noise Examples
29:40 Conclusion
30:26 Multitrack Recording