Shattered Kingdoms

Are you ability to concentrate on songs dependent on how many people are attacking you?

Concentration in general is affected by being in melee so I would think that is also true for songs, never played a Bard though....

It is dependent. I think it is damage in melee you receive and not the number of people you fight.

Do you pre-damage reduction or post damage reduction? If it is post damage reduction, there is something wrong. I was taking no damage and my concentration was being broken

For every individual you are in combat with, it drops your concentration slightly.

Whenever you take a substancial amount of damage, such as "THAT HURT A LOT!" kind of message, or from spells such as flamestrike or hellfire, you have a significant, but only momentary, drop in concentration.

This can prevent you from casting, stop you from singing, stop you from dancing, make you lose concentration on current spells.