I allow a modest warning, though, since I had already several theremins made by Golem in my hands and in my repair shop. These instruments are NOT AT ALL suited for the classical or precision player. There is no coherent tone spacing, linearity (which linearity?) is more than poor. These instruments have theoretically a huge pitch range of up to 9 octaves and many knobs to fiddle around but it is impossible to set up the pitch field to have at least more than one octave with decent (and thus precisely playable) spacing between the tones.
This is IMHO due to the fact that all the GOLEM instruments are based on the digital variant of the so-called Glasgow-Theremin, the result of a theoretical paper, published many years ago by the university of Glasgow, which was a description of a digital concept where the signals of simple and unstable CMOS RC oscillators undergo frequency to voltage conversion before being fed into a simple one-chip function generator of the 2206 type. Musical needs are nowhere respected in this circuit, the poor response of the RC-oscillators is directly transmitted by the V/Hz-style f-to-V conversion and fed into the generator chip without any linearization or exponential correction.
In my eyes, the Poseidon 4 is a cheap experimental toy which sells for 99€ and isn't even worth that. The statements on the Golem website "pure sine wave, even in the deep bass range", "extended pitch range from 100 to 18000Hz", "On the idea of the Glasgow-Theremin were developed several models to the current models ..." show that these noise generators have been designed by technicians which haven't ever talked to professional thereminists to see what are the needs of a true musician.
I was several times in the uncomfortable situation where people came to see me with their Golem theremins and wanted me to "fix it" or to "make it playable". After spending hours of analyzing that stuff, I finished always up replying: "Get rid of it and buy a true theremin, a Moog or a Subscope".
