There is nothing odd about the SY77. I see you also have a FS1R. I haven't used one of those but I'd imagine the Advanced FM with the extra algorithms is probably also the same in the FS1R. The SY77 is a great synth. Very much the update to the DX7II. The digital samples are very early and lores but still useful to layer with the FM voices. The SY99 is basically the same engine but adds sample memory and improved onboard FX. I would really like to pick up a FS1R myself as it sounds like the ultimate FM synth.