Mammoth Bellow

Tapping a creature won’t reduce colored mana components of harmonize costs.

You must still follow any timing restrictions and permissions, including those based on the card’s type. For instance, you can cast a sorcery using harmonize only when you could normally cast a sorcery.

To determine the total cost of a spell, start with the mana cost or alternative cost (such as a harmonize cost) you’re paying, add any cost increases, then apply any cost reductions (such as the cost reduction from tapping a creature). The mana value of the spell is determined only by its mana cost, no matter what the total cost to cast the spell was.