There were several other morphing z-planefilter synths from Emu. The UltraProteus (1U rack module) was the same generation as the Morpheus, but with more conventional Proteus sample ROM sounds (trumpets, pianos, etc.). The Emulator 4 series samplers implemented z-plane filters with only two variables (one note-on, one real-time... the Morpheus had a third, note-on variable). The Proteus 2000 series (1U rack modules... includes Mo'Phatt, Xtreme Lead, Orbit-3, Planet Earth and others) implements the same 2D version of z-plane filters as the Emulator 4. The Emulator X software sampler and Proteus X software sample player implement z-plane filters with three real-time variables.And Rossum Electro-Music now offers the Morpheus eurorack digital filter module, with three morph controls.