Here are two related questions, actually.
1st: What action type (time) does it take to pass an item from one hand to another (assuming the other hand is free)?
2nd: I know that retrieving or stowing an accessible item is a minor action, but how much time (action type) does switching items in hand take? With switching items I mean, for example, passing a weapon wielded in my main hand to my off-hand and, simultaneously, passing the implement in my off-hand to my main hand.
Thank you.
I don't believe there are written rules to address this.
However, I would consider both actions you describe as roughly equivalent to retrieving an item from a pouch, and therefore say that it costs a minor action.
As for how long it takes in "real-time", the most accurate statement anyone can make is that it would take no more than six seconds - which is the approximate time given for one round of combat. With the exceptions of rests, rituals, and travel across distances, most actions do not have any rules stating how long they take to complete.
This does beg the question though, "Why do you need to do this?". As far as I'm aware, there's no effective benefit or penalty for using one hand or the other for most purposes.
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.
While I agree with Iszi's answer about it not really mattering, I have always considered moving an item from one hand to another available hand to be a free action. I would expect switching hands to be similar to drawing a weapon, so a minor action.
Is this a simplification of the real world? Yes, but so is D&D.
Switching an item from one hand to the other (free) hand is a free action.
To switch items in hands: Drop one item (free action). Pass item from hand to hand (free action). Pick up dropped item (minor action). Total: 1 minor action.
I didn't think much about these rule until the Ranger in my group switching from bow to axes with no penalty, so I made her drop the bow or spend a move action to put it away.
I'd say a move action or thereabouts -- try it sometime with a drumstick and a really sharp knife, while someone tries to punch you. It's not easy.
But Iszi is right -- the rules don't require that your implement be in your "good hand," just that it be in hand.
