  We will prove a Moser-type theorem for self-dual harmonic 2-forms on closed
4-manifolds, and use it to classify local forms on neighborhoods of singular
circles on which the 2-form vanishes. Removing neighborhoods of the circles, we
obtain a symplectic manifold with contact boundary - we show that the contact
form on each S^1\times S^2, after a slight modification, must be one of two
possibilities.
