Cures silence.Final Fantasy description
Vox allows a non-silenced user to remove the Silence status effect from a party member. The animation of the spell is a reverse to the Silence spell. In both the original and the Zodiac versions, the License for Vox is White Magick 2, which takes 20 LP to unlock.
The spell initially takes 8 MP to cast and can be purchased for 300 gil from shops Dreadnought Leviathan onwards in the original version, but in the Zodiac versions, Vox is available since the game's beginning and can be used by the White Mage and the Red Battlemage. It is also a Diamond Armlet treasure on Stage 21 of Trial Mode, and Larsa joins as a guest knowing the spell.
Vox is a White Magic ability with a Rarity of ☆. It removes Silence from one target, it can initially be used four times and it can be honed to Rank 5. It can be created by using Minor White Orb x3, Minor Ice Orb x3, and 1000 gil.
Behind the scenes
During the development process and original Beta for Final Fantasy XI, the game's Silena White Magic was originally named Vocal (ボキャル, Bokyaru?), which is the Japanese name for the recurring Vox White Magic spell. For the official release, the spell was changed to Silena, to match the naming scheme for the other status healing White Magics. 
Vox means "voice" in Latin.