rare birds: Hillwood SY-1800 monophonic synth

Extremely rare japanese synth from the early 70s. No information available online, so if you have some please comment. There is already a video demo focusing on the dark (shall i write darth ?) and experimental side of the synth so I decided to show the more melodic side of the instrument. Recorded with no EQ nor treatment except for a tad of reverb. This is probably the rarest and strangest bird I’ve met. You may think it’s a kind of simple monophonic analog 1 oscillator synth like the Roland SH 2000, but there is more than meets the eye. It took me some time to understand what’s going on and to this day I am still not sure exactly how it works but it looks like the oscillator is a kind of very early FM based oscillator. Check the video, especially the “bell“ presets and you’ll know what I mean. Tone is shaped by 3 faders labelled “Fundamental“, “Overtone“ and “Brillance“, and these are interconnected. There is a simple envelope which works as attack decay (labelled “attack“ and “sustain“) by default but can be switched to attack release by the push of a button (“sustain long“). Funny thing is the attack fader is inverted compared to classic synth topology: when raising the fader the attack gets shorter. All the presets have their own envelope setting and depending on the presets the attack and decay faders do not behave exactly the same, ie the envelope faders do not totally overide the presets envelope. You can also have the envelope assigned to the filter by switching on “VCF expand“, and control the envelope to VCF amount with the “Expand“ fader. The “Expand Envelope“ seems to invert the VCF envelope. It’s quite efficient on some presets and not on others. “Touch portamento“ switch is actually a key retrigger option. When activated envelope retriggers on every key stroke (low note priority) otherwise the envelope is legato. So it has nothing to do with the “portamento“ fader which is indeed a portamento effect. “Gride“ is basically a pitch bend (upwards only). “Growl“ switch adds... growl: it adds a kind of brassy attack to the sound. Not efficient on every preset but can add to the realism of the sound on others. There is also a LFO which can be delayed (it’s more like a slow attack then a proper delay), consisting of either pulse or triangle wave shape, that can be assign to “vibrato“, “wow“, “chorus“, “tremolo“, and you can have the envelope repeat on the lfo speed thanx to the “repeat“ switch. And finally there is a noise generator with dedicated fader level and a “Noise only“ switch that is self-explanatory. This makes for a uncommon and interesting monophonic synthesizer. Very expressive in my opinion, once you managed to tame it.