Watch out, something weird falls in through the hole. What is it? It's a Yamaha CS-20M!!!

Judging by the size, by the year, and by the technology, this synth should be very fat & organic sounding, but somehow it isn't. The sound is in a way massive, but at the same time very humble and aloof. Did you ever wodner why the CS line is (relatively) cheap? I did, and I think it's because it sounds too "perfect". As if the engineers at Yamaha had been too good at taming the analog instability (a quality perceived as a downside back in the day), and now people interpret the results as "characterless".

The CS-20M has only one LFO, which is the biggest disappointment in this synth, but this LFO has several shapes, and the shapes can be changed independently at the destination. It means that VCO1 can be modulated by a sine wave, VCO2 by square wave, VCF by sample & hold and VCA by a triangle wave simultaneously. Next uncommon thing - the memory. It doesn't work the way typical memory circuit does, because when you save a patch, you don't actually save the sound itself, but freeze the control panel, as if. It means that you cannot edit a patch once saved, apart from some basic controls like PWM, Cutoff, Tune, Glide Time. Actually this method is quite bad, because what is the use of having a memory if half of the knobs / settings are not included in the saving process? Another big disappointment in this synth.

The ADSR module (the envelope) is specific; there's a switch that enables you to choose "normal" or "time x 5". This changes the time span of the envelope, making Attack, Decay and Release settings more precise. Next thing is the badass subbass sinewave; the frequency of the sine generator is controlled by the tune value of VCO1, just too bad it's placed after the VCF block and you can't filter it. Of course Vangelis-and-CS80 fans will thank Lord for this kind of arrangement.

I started off with a grudge in my tone, but I have to conclude that CS-20m is one of the most interesting and magnetic synths I had the opportunity to mess with. Big, sturdy, lots of knobs, rare. To put it simply - an individuality. It may not satisfy the majority of musicians, but it will surely satisfy every collector of original synths.

OK, some technical details, as this model is quite rare and unexplored:

- LFO [Repeat / Trigger]
- VCO 1 [Feet 64'-2', Triangle, Saw, Pulse with PWM, Pitch modulated by sine, saw down, saw up, square, s/h, glide up, glide down]
- VCO 2 [the same]
- Noise Generator
- Multimode VCF [LPF, BPF, HPF], Cutoff modulated by sine, saw down, saw up, square, s/h.
- ADSR for VCF with inversible polarity
- ADSR for VCA
- VCA with sinewave generator, Initial Level control, Amplitude modulated by sine, saw down, saw up, square.
- Portamento / Glissando
- Trigger In/Out
- CV In/Out
- Program-Tape In/Out