Is Explosive Singularity legal in Standard, Modern, and Commander?

Explosive Singularity is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Explosive Singularity

Q: What type of card is Explosive Singularity?

Explosive Singularity is a Sorcery. Its oracle text reads: "As an additional cost to cast this spell, you may tap any number of untapped creatures you control. This spell costs {1} less to cast for each creature tapped this way. Explosive Singularity deals 10 damage to any target."

Sorcery

As an additional cost to cast this spell, you may tap any number of untapped creatures you control. This spell costs less to cast for each creature tapped this way.