The Japanese SMS does have the YM2413 chip clearly seen in the above image ( Large scan ). Right next to the main Z80 NEC CPU and the Sega Chip. While researching this I came across a great site. http://www.smspower.org/maxim/ .Lots of interesting music hacks and hardware docs for SMS.
SN76489
YM2413
YM2612-Used in Coin Ops and Genesis.
As it turns out Genesis has the YM2612 FM chip along with the PSG SN76489, Go figure. If anyone is curious as to programming the PSG the following link has a great tracker program made just for that. http://mod2psg.kontechs.de/ However I am just interested in sending a bunch of random binary data to it and seeing what it comes up with.