Stat Modifier for Missed Bard Notes Question

[Grimmly Fireforge]

According to Character Creation Screen, both DEX and CHA stats affect the chance to fizzle/miss notes. I always read it was just Dex. Here are my questions:

1. Is it true that both stats affect it and not just Dexterity?
2. If true, how does this work? Does it average the two stats? Take the higher of the two stats? Take the lower of the two stats?

Character Creation Screen

Dexterity affects your chances for special melee abilities such as combat effects and critical hits. It increases your chances to gain points in most combat skills. It is also a factor in determining how much damage you do with throwing weapons and archery.
Bard Only: High dexterity decreases the chance you will miss a note while playing a song.
Tradeskills: If your dexterity is higher than your intelligence or wisdom, it determines how quickly you gain skill in Fletching and Make Poison.

Charisma affects how much merchants will charge you for their wares. It also affects the chances for charm, memory blur, mesmerization, and divine intervention spell effects to work.
Bard only: High charisma decreases the chance you will miss a note while playing a song.