###Maybe
Maybe
Generally you can, but there's one big exception. You can only ever use one free action to make an attack per turn, regardless from what source that attack comes.
Free Action[DDI]:
Free actions take almost no time or effort. You can take as many free actions as you want during your or another combatant’s turn. There is an exception to that rule: A creature can take a free action to use an attack power only once per turn. Creatures don’t normally have attack powers that can be used as free actions, but some powers and other effects grant the ability to use an attack power (usually a basic attack) as a free action. For example, a character might have two different abilities that let him or her make a melee basic attack as a free action when their respective triggers occur. If both abilities are triggered on the same turn, the character can make only one of the melee basic attacks during that turn. [...]
From my reading you could use the Harmony Blade's critical entry as many times per round as you wanted provided you score the required critical hit. However, all other options to attack that can be used as a free action would share the same 1/turn free action attack limit and couldn't be used in conjunction.
Even with no actions, the main-hand trigger requirement on the following two would mean they can't trigger each other. Rampage can trigger a free attack that can trigger one of the other two, but the other two can not trigger each other because they are made with the off-hand weapon.
