HT-6000 was developed by Casio Computer Co. Ltd., Released in 1987
The HT-6000, released in late 1987 but not widely available until late 1988, was an entirely different SD synthesizer which greatly expanded SD the synthesis engine. While designed as a consumer model, it was far more powerful than the more professional-appearing HZ-600 whose synthesis engine the other HT’s utilized. The HT-6000 introduced for the HT line some of the more high-end features previously only included by Casio in the CZ line, such as ring-modulation, detuning, key-follow, and initial-touch (which, among the CZ’s, was only found on the most advanced model, the CZ-1). The HT-6000 used an impressive 4 DCO’s per voice (vs. 1 on the other SD synths, and 2 on the CZ synths). It had 64 DCO wave forms to choose from (32 basic, 16 with noise [white or metallic], and 16 with ring modulation). It had 8 independent VCF filters (1 per voice, vs. 1 per channel), and added key-follow parameters for both the DCA and VCF. The DCA also added attack and decay curves (acute and obtuse). It also added an independent ADSR envelope for noise. The 4 DCO’s each use the same waveform, VCF and DCA envelopes, but can have separate tunings, velocity response curves, and relative DCA envelope depths. Stacking the oscillators with detunes allowed the creation of flange and chorus effects, fat “super saws”, and the creation of dual-note or even triad and 4-note leads. The filter cutoffs could be set to respond to velocity which added some expressiveness. Because each oscillator could have separate tuning and velocity response, it was also possible to have the pitch change according to pressure, if one of two differently tuned oscillators had an inverse velocity curve. Ring modulation used oscillator 4 to modulate oscillator 3, and allowed the creation of metallic and pulse sounds, lower bass harmonics and even distortion. Like the HZ-600 but unlike the others, the HT-6000 had a complete parameter list silkscreened on the outer panel, somewhat alleviating the need for a manual. In terms of “home keyboard” features the HT-6000 improved the auto-accompaniment versus the previous HT’s by including some additional PCM drum sounds, an additional accompaniment part (obbligato), 4 bass patches (versus one), additional chord inversions (including more tonic, suspended and subdominant triads), and the addition of “Intro” and drum and chord “Variation” for auto-rhythms. The HT-6000 was also sold in Germany by Hohner as the KS-610/TR.
The HT-6000 was reviewed in Keyboard Magazine, November 1988, p. 149. If the HT-6000, rather than the HZ-600, had been packaged as the “professional” model, it may have sold much better.