Bards and Instruments, HELP!!

[Mono-Tone]

Ok so I am almost 56 and still rocking my store bought instruments like a champ!
This is the first time playing a bard and I dont quite understand how much the multipliers are. I can see that putting the correct instrument for my AE spells, doubles the damage. But what is the difference of say Han Drum and Selo's Drum of the March. I've looked and looked but could not see the difference as it relates to actual number multipliers. say I am doing 34 dmg per tick with my AE how much dmg would I do with the Selo's Drum.

Please no flaming, serious shit here!