4x bard does 60 base
3x does 48
2x does 36
Discord Grants 5 damage per 10 points starting at 90. (So 90 = 5, 100 = 10, 110 = 15, 120 = 20)
Musicianship 4 damage per 10 points starting at 90 ( So 90=4, 100=8, 110 = 12, 120 = 16)
Each additional skill adds 4 damage per 10 points starting at 100 skill.
Damage modified by 1.5 versus Non-Players
Slayer doubles that modifier to 3x
VS Players Magic resist reduces the damage by up to 40% (I think) so 4x would do 36 damage vs 120 resist
For tribulation
Musicianship grants the proc Chance and Discord affects how much bonus damage is dealt.
36% @ 2X 120 with a 60% Proc Chance ( I think)
@4X its 50% bonus damage, 84% proc chance
With a slayer bonus damage receives a 1.5x modifier
Not sure about magic resist in PvP off hand, cant remember right now, it might not affect Tribulation at all other than allowing the target to shake off the spellsong.