Simple bard question with simple answer!

[TaneshimaPopura]

Songs do affect the singing bard, battle voice also affects the singing bard. Your MP will almost not dwindle with Ballad paired with Battle Voice. Battle Voice should be used only for 2 scenarios : Recover 25% of Healers MP, expecting a burn phase when you have a Black Mage in group with Requiem.

In any other situation outside where there the above 2 situation doesn't occur. Don't use Battle Voice, and only requiem till 50% of your MP and toggle it off and on when you're almost full again.

[RyuujinZERO]

Battle Voice should be used only for 2 scenarios : Recover 25% of Healers MP, expecting a burn phase when you have a Black Mage in group with Requiem.

*facepalm*

I'm guessing you missed the bit earlier that suggests requiem earlier broken and doesn't affect elemental, but untyped magic damage (ie. SMN/SCH dots, ruin, WHM holy. But doesn't affect BLM spells, WHM stone, aero)

[Bardo]

... and doesn't affect elemental, but untyped magic damage (ie. SMN/SCH dots, ruin, WHM holy. But doesn't affect BLM spells, WHM stone, aero)

Seems like there is still some confusion about how Foe Requiem is working.
Let me see if I can attempt to clear that up.

Foe Requiem works for all BLM spells, SMN/SCH damage, WHM holy, stone, aero, etc...
It works for elemental damage, magic damage, AND unaspected damage.

However, here is where the confusion seems to come in:
There are a lot of tooltips in the game that say "fire damage" or "wind damage" such as Windbite or Dragonfire Dive... THESE tooltips are wrong.
These Bard/Drg "elemental" attacks ALL apply as physical damage, and therefore do not get boosted by Foe Requiem.

This is easily tested by firing any of these skills at a Soldier on Turn4.
The soldiers have a stoneskin against all physical damage, and that stoneskin will absorb Windbite, Venomous Bite, Flaming Arrow, Dragonfire Dive, etc...

So once again, Foe Requiem works for all damage done by DoM jobs, but it doesn't affect any attacks from DoW jobs.