At its heart the MT-400V has some fairly standard Casiotone rhythms and voices, but someone had the bright idea of giving the user control over the analogue filter envelope (attack, sustain and decay), cutoff and resonance. As well as applying this to the voices, you can also filter the rhythms and auto accompaniment. There's a stereo chorus with adjustable speed which can be switched to act like an LFO modulating the filter, an effect which Casio quite accurately describes as Waw. Add in bass and chord variations and analogue drums and you've got a great little lo-fi synth and groovebox.