For musical notes? To tell the truth--I'm not sure.
But as for most special symbols, use shift, control, alt, or a combination of them on various keyboard buttons and see the results. There are lists of some of the commands, no doubt, but many of these vary between programs (and games) so you could probably find out by trial and error this way.
That SOUNDS like ascii, but when I tried the number combos found at the bottom of THIS page, (for instance holding the alt and pushing in 171 on your number pad should produce ½) they didnt work within guildwars. So it's not ascii >.>