There are no rules for handedness in 4e. While there are rules for "off-hand" weapons, the rules explore the use of dual-wielding weapons. Therefore as handedness doesn't matter, "swapping" the contents of your hands has no rules impact and is therefore flavour. You may choose to sacrifice actions to make it look showy, but that is also a flavour thing.
As an important note, the tossing your sword into your other hand and saying (from the Princess Bride):
Inigo: I admit it; you are better than I am.
Man in Black: Then why are you smiling?
Inigo: Because I know something you don't know.
Man in Black: And what is that?
Inigo: I am not left handed! [switches sword to his right hand & they continue fighting, with Inigo winning]
Is a standard action, because it's using the sword as a prop for intimidate.
Now, with that said, there are times when you may want to rapidly swap equipment between the "used" and "unused" states. Swapping between "main-hand" and "off-hand" as noted doesn't take any time. One method for rapid-equipment swapping is the Disembodied Hand familiar which grants, as a constant action:
You can retrieve or stow an item as a free action instead of as a minor action.
Note, however, that you can only take one free action on your turn, so stacking these isn't particularly useful.
A deep-pocket cloak has a similar mechanic, as well as being incredibly flavourful.
If you want to swap weapons, there is nothing better than the feat Master at Arms. If you want to swap implements and weapons, you'll need one of the prior mechanisms and the Quick Draw feat. (Tieflings have an ... interesting option of the Clever Tail feat, mainly for flavour.
For a bard to swap rapidly between implements and weapons, not counting weapliments like the songblade, or feats such as "arcane implement proficiency" or multi-classing swordmage, you don't often use minor actions, so any one of the above items or feats should work.