The mda DX-10 VSTi is a freeware FM synth that recreates the classic FM sound but with a much simpler and more intuitive interface than any DX synth, or any of their software imitations.
By using a harmonically rich modulating oscillator (with extra control in
the new version) only only one carrier and modulator produce a wide range of FM sounds typical of the later series of Yamaha DX synths such the DX-11 and TX-81Z.
Download this free VSTi here
Check out the new (commercial)
VSTi & DXi versions of the mda DX-10 here.