Harmonic Waves is a Normal Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Harmonic Waves is Unlimited.
YGOPRODeck lists Harmonic Waves for these formats: Duel Links, Common Charity, TCG, OCG, Master Duel.
A listed print of Harmonic Waves appears in Starter Deck: Dawn of the Xyz (YS11-EN022) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Harmonic Waves is about $0.10 on Cardmarket (prices change frequently).
