Harmonic Oscillation 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 Oscillation is Unlimited.
YGOPRODeck lists Harmonic Oscillation for these formats: Duel Links, Common Charity, TCG, OCG.
A listed print of Harmonic Oscillation appears in 2016 Mega-Tin Mega Pack (MP16-EN028) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Harmonic Oscillation is about $0.05 on Cardmarket (prices change frequently).
