Zephyr Singer

You can't tap more creatures to convoke Zephyr Singer than is necessary to pay for the spell. In most cases, this means four creatures. However, if there are any additional costs to cast Zephyr Singer, you may use convoke to pay those additional costs as well.

When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn't change a spell's mana cost or mana value.

Tapping an untapped creature that's attacking or blocking to convoke a spell won't cause that creature to stop attacking or blocking.