Yamaha make a couple of soft synths - the S-YXG50 and the S-YXG100. You can get a free download from Yamaha for a 90 day trial. Version 4 of the S-YXG50 offers a 4 Mb set of samples. I have version 3 which has only 2Mb. It only does XG level 1 - 480 voices, but has a TG300B mode (676 voices) which I've never used. It also comes with a midi player. There's not much you can do with it except run it from a sequencer which I do, using XGworks. I have it installed on my laptop and it saves me lugging around a keyboard if I want to check out a sequence. It has a very high latency so isn't really useable with a keyboard, regardless of the speed of the CPU.

Bryan