Actually, watch this firiona one.
https://www.youtube.com/watch?v=jV1AsERU4RM
Around 6 minutes I start blabbing about the instrument modifier and how when you place the item into the slot you can still get full damage after it fires. This is a bard still at 43.
At level 43, a bard will be able to do 53 damage per tick (24+29)
At level 47, a bard will be doing 57 damage per tick (26+31)
At level 48, you add in a third song, and can do an additional 52 damage for a total of 109 damage per tick if you nail all instruments perfectly.
I'm not the best swarmer and when I used to do that I did the stupid drive by method for newbs. A good circler who's perfect can do a lot of damage.
I also learned that chant stacks can allow a bard to get up to 70 DPS at the end of the game, but I only stopped at level 56, no epic, and not that crazy long duration chant