The Soloist 505 is a very simple monophonic synth. Its look reminds one of a Roland SH-1000, but with its controls on the front. To make the organ-look complete it has a really ugly sheet-music stand. The sound is very clear and clean like many Italian cousins (Siel). There is a preset section but the waveforms can also be modified in 'free' mode. Don't expect any huge sound experiences out of this heavy thing. But the keyboard is good and there are some presets such as the sax and trombone which have some power worth exploring. It's cute and slightly rare - but don't pay any big money for it. No MIDI or CV here.
The unit features 11 Presets like Brass, Oboe, Trumpet, Hawaiian Guitar, Cosmic, Flute, and more. A variation mode makes the instrument more versatile by giving some user control over the attack, filter, and a few other parameters.
A feature of the Soloist 505 is that it has the famous Moog Ladder Filter onboard. Manufacturers installed the components to make the Ladder Filter before Moog Music imposed a patent on it's use in non Moog instruments.