Earth resistance stacks with other Carol effects.
Equipment that gives "Carol +" or "All Songs +" does not increase total bonus to Earth resistance, but does increase the duration of the song by 10% for every +1 granted.
Elemental damage nullification of Carol II songs has a measured base value of approximately 15% 
"Carol +" or "All Songs +" equipment does increase the chance of damage nullification by approximately 10% per +1 granted. For example, +6 to Carol gives (15% x 1.6) = 24% chance of damage nullification. Soul Voice also increases the chance of damage nullification, but will not push the chances past a measured cap of 40%. 
How to Obtain
|Auction House Category: Scrolls > Songs (||)|
May drop from coffers
Drops from tier 2 and higher bosses in Scars of Abyssea zones.
Can drop from Zilart and Promathia era battlefields.
May drop from Chapter I and above encounters.