As always when it comes to "preset synthesizers" the CS15d is usually overlooked. The Synth is one of the last Yamaha monophonic Synthesizers-range (manufactured from 1979-1982, I think) and was phased out shortly before the DX7-craze-bells-mode went completely through the roof. This is why the CS15d is forgotten, I presume. This is sad because you can get A LOT out of this small and beautiful machine. The 29 presets alone are sounding good. It´s true analogue and due to combining and mixing possibilities (and the tuning knob in between the two channels) there is already a lot to discover when you tweak here and there. The last preset is called "manual" and by pressing it, it unfolds the Manual-block on the right of the CS15d. This is a full blown VCO, VCF, VCA block which affects one of the two preset - "channels". The other channel still represents a chosen preset, which you can now mix or combine with your own programmings. I love the clear sound of the CS15d already but when you combine it with some fx this synth sounds mighty. My CS15d runs through a full loaded Yamaha SB-200 board and the combination of these two units is a sound universe for many years to discover. Definitely a well underrated synth!