As is well documented, Yamaha never addressed the bugs in the vocal harmonizer on the PSR2000, even though Steve was kind enough to find a work-around for it.
Even though all the other models worked correctly, Yamaha insisted that the 2000 was supposed to be as it was.
Oh, by the way, they did fix it in the 2100, which should never have been produced--it should have been done by a software update to the 2000 OS. Oh, that's right, they couldn't update the software because the OS was on a chip, contrary to what Yamaha advertised.
DonM