Is Crescendo of War legal in Standard, Modern, and Commander?

Crescendo of War is legal in: Legacy, Vintage, Commander.

Crescendo of War

Q: What type of card is Crescendo of War?

Crescendo of War is an Enchantment. Its oracle text reads: "At the beginning of each upkeep, put a strife counter on this enchantment. Attacking creatures get +1/+0 for each strife counter on this enchantment. Blocking creatures you control get +1/+0 for each strife counter on this enchantment."