When Kawai released the SX-240 in 1984, it arrived at exactly the wrong moment—the digital synth revolution was in full swing and marketing budgets were thin. That timing meant this eight-voice powerhouse got overlooked for decades, which is a shame because it's genuinely one of the most capable analog polysynths of its era.
The SX-240 packs two digitally controlled oscillators plus a sub-oscillator per voice, giving you a thick, wide analog character that rivals machines costing significantly more. The filter is where things get really interesting: it uses the same SSM 2044 chips found in the original Prophet-5, delivering that creamy, musical filter character that defined an era. You get poly-8, poly-4, and mono modes, and in mono mode you can stack all 24 oscillators together for an absolutely massive sound. The control layout uses a dedicated data wheel with four scroll buttons for parameter editing, similar to the Roland Alpha Juno, with an LED indicator showing what you're tweaking. A big electroluminescent display lets you name and save your 48 programmed tones using the keyboard itself. There's also a built-in sequencer with eight memory slots, a BBD ensemble chorus effect, and both portamento and glissando for expressive playing.
The SX-240 was ahead of its time with MIDI implementation—it has IN, OUT, and THRU terminals and responds to all MIDI channels. The 61-key keyboard includes a pitch bender and modulation controls, and the whole thing is surprisingly compact for what it can do. Collectors and players who've discovered this synth tend to rave about its sound character and the fact that it offers eight voices when most competitors of the time maxed out at six. The main criticism you'll hear is that modulation options are somewhat limited compared to deeper analog designs, but that's a minor trade-off given the filter quality and overall sonic capability.
