Spellbinding Soprano + Sprout Swarm + Young Pyromancer

Prerequisites

You have at least three opponents. You control an untapped green creature.

Steps

1. Activate Spellbinding Soprano's encore ability by paying {3}{R} and exiling it from your graveyard, creating two token copies of it with haste for each opponent you have.
2. Declare each Spellbinding Soprano token as an attacker.
3. Each Spellbinding Soprano token triggers, causing instant and sorcery spells you cast this turn to cost {1} less to cast for each Spellbinding Soprano token.
4. Cast Sprout Swarm with buyback by tapping a green creature and any other creature you control.
5. Young Pyromancer triggers, creating a 1/1 Elemental creature token.
6. Resolve Sprout Swarm, creating a 1/1 Saproling creature token and returning Sprout Swarm to your hand.
7. Repeat from step 4.