CASIO HT 3000 WITH ANALOGUE FILTER

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"The Casio HT and HZ series are a very interesting group of synthesizers produced from 1987-1991. They use a very specific form of sound generation called "SD Synthesis". Short for "Spectrum Dynamic" SD Synthesis has some things in common with the subtractive synthesis we know and love. The synth takes a waveform and runs it through a real analog VCF (filter). There are ADSR envelopes for the DCA and VCF that shape the sound. And there is an LFO just like on a standard subtractive synth, although this LFO only modulates pitch (vibrato) and volume (tremolo). Where things get interesting, is in the choice of waveforms available from the synth engine. There are 32 incredibly varied waveforms, some sound very nasal or narrow, some like saw or square waveforms, some with an odd metallic timbre, and some feature white noise. It's still a mystery exactly how these waves are created, but experts suggest they contain a number of harmonically-rich pulse waves at different octaves, as well as a ring modulator and an analog noise source. To make things even more interesting, these waves have pre-programmed amounts of PWM and amplitude modulation built into them. For example, one SD wave could contain two pulse waves fading in and out at different times. But you don't have to understand all of this to get the best out of the synth. The mystery and modulation of it all means you can just pick a preset and change the waves around and see what happens. The synth sounds are in the same ballpark as other DCO-synths of the time, and can even sound a little PPG-like on a good day. The filter is great and adds a nice swoosh to some sounds, plus there is also a nice chorus effect on board. Additionally, being a home keyboard, it has built-in speakers, a Drum Machine and an Auto-Accompaniment mode (the lower tone is used for accompaniment). The drum sounds resemble the Casio RZ-1 8-bit drum machine."