Choir of heaven

You may tapp seven humans or four angels rather than paying this spells mana cost.
Opponents creatures get -2/-2 and lose all keywords and mana abilties.
If you control 7 or more plains you may draw a card as you tapp Choir of heaven.
{t}Add{w}{w}, gain 3 life, scry 2 and create a 4/4 Angel with flying