[The Alpha Bat]

Simply build SAN. The whole point is that getting sanctity makes you more pure and thus eliminates your corruption traits.

I will direct you to a quote of mine just a few posts up.

I've yet to see a compelling lore reason why corrupted races are worse at hurting things with sound magic than others.

Of course, that's entirely an issue with SAN being connected to Sound ATK.

Lest we forget, for the actual issue of the matter, here's the three most important facts:
1. Sound ATK is required to utilize Dark Bard well relative to other players.
2. Building SAN is required to raise one's Sound ATK to the aforementioned competitive level.
3. Building SAN negatively impacts corrupted races' racial abilities.

The addition of a Luminary Element Sound would be a janky solution but indeed a solution. Currently, this is both a balance issue and a lore issue.

Before it's said (again), yes, there's nothing inherently wrong with a race being worse with a class than any other race but the game currently does not work like that, at least not to this extent. And that's ignoring the difference between some races being better with a class and some races being worse with a class. Now, this could be a first in the way the game is designed going forward but, frankly, I'd rather not be heading in that direction. I want my race/class freedom.