Useful Links:

http://web.quick.cz/a.tom.x/dxage.html A whole host of individually profiled Yamaha FM synths are listed here, from DX7 to YS200. Not the most comprehensive site out there but there's a lot of "synth profile" data.
http://sounddoctorin.com/synthtec/yamaha/dx27.htm The Synth Doctor. Plenty of technical info here as well as service info etc.
http://www.musictechnologiesgroup.com/ Backlit LCD's on older equipment.




UPDATE:

March 9, 2025: We had to weed a lot of links out of the links list. Sorry to have had the list fulkl of dead and/or bad links for so long.



User Contributed Links:

Have a link to some good 4OP related info? Leave us a comment on our Facebook page and we'll consider adding it!