2005-10-01 : Chorus of the Conclave’s ability applies to creature spells only as they’re being cast. You can’t pay mana to put counters on creatures being put onto the battlefield by an effect.

2005-10-01 : Chorus of the Conclave’s ability combines well with the convoke mechanic, effectively letting you tap creatures to put +1/+1 counters on the creature with convoke that you’re casting, if you choose to do so.

2005-10-01 : Chorus of the Conclave’s ability works only while it’s on the battlefield, so you can’t use it to put +1/+1 counters on itself.

2021-03-19 : If a creature you control has a mana ability with {T} in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell’s costs. You won’t be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won’t be on the battlefield when you pay the spell’s costs, so you won’t be able to tap it for convoke.

2021-03-19 : 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.

2021-03-19 : You can tap any untapped creature you control to convoke a spell, even one you haven’t controlled continuously since the beginning of your most recent turn.