Heh, that's an exaggerated example. Sure, dwarves can be defined as not having good enough command of their voice to affect their audience to that extent (which appears to be how they're viewed), but all I'm saying you could equally well say that they DO have that capability. Their max charisma even translates to "charismatic", which suggests an above average presence/influence. I've never imagined dwarves as non-singers, quite the contrary, while not reaching the wide vocal range of humans/elves, they still sing with strong, deep baritone or bass voices. In game terms this difference would translate to slightly less effective songs.