I recall there's a Dreamcast disc image floating around somewhere with a different music selection. Depending on where you got your copy of Rez, who knows what you've got. :)

I just pulled my dreamcast out to play some of the games with my son. It's still a great system. There are some low quality games, but it definitely feels like you have to seek them out; as opposed to the shovel ware feeling I get on the PS1/PS2. Looking at the released game list though, I feel like some of these titles were probably good at the time, but won't hold up; but many of them are still as good as they were. VGA output is pretty nice too.