Conductor of Nature's Concert

Creature spells you control gain Convoke.
{1}{g}{w}: Populate, use this only as a sorcery,
no more than once a turn.
{x}{x}{g/w}{g/w}{t}: Create a X/X green token creature.
It is a Saproling if 1/1 and a Centaur otherwise.
You may pay one option to change the token:
• {g}: a Wurm with Trample.
• {g/w}: a green-white Elf Knight with Vigilance.
• {w}: a white Bird with Flying.
"All life sings her song."