The JD-990 is an enhanced version of the JD-800 and was the top o' the line JD-synth. Its rack-mount design and impressive power and functionality within the studio paved way for the hugely successful JV-series rack modules which lead, ultimately, to the XV-series monster-modules! The JD-990 is a digital synth with 6MB of ROM sounds with "analog-like" edit parameters and features. These include lowpass filtering, ring modulation, osc. sync, frequency cross-mod, etc. The JD-990 is also compatible with JV80 and JD800 expansion boards.