DXi FM Synthesizer started off life as a faithful recreation of the Yamaha DX7, and was infinitely easier to program than the original hardware. After constant development and updates, DXi far exceeds slavish emulation, and has become a very modern instrument. First with the inclusion of a delay and a low-pass filter (uncommon in FM Synths). Now it even sports multiple waveforms instead of the typical sine-only FM synths or yore. If you've ever thought about getting a DX7, spend all of that money on a solid MIDI controller instead and then spend $2 on this. FM Synthesis is a complicated and chaotic subject though, so it is not for everyone.