We consider a dual pair (G, G ′ ), in the sense of Howe, with G compact acting on L 2 (R n ), for an appropriate n, via the Weil representation ω. Let G be the preimage of G in the metaplectic group. Given a genuine irreducible unitary representation Π of G, let Π ′ be the corresponding irreducible unitary representation of G ′ in the Howe duality. The orthogonal projection onto L 2 (R n ) Π , the Π-isotypic component, is the essentially unique symmetry breaking operator in HomWe study this operator by computing its Weyl symbol. Our results allow us to compute the wavefront set of Π ′ by elementary means. Contents 1. Notation and preliminaries. 4 2. The center of the metaplectic group. 5 3. Dual pairs as Lie supergroups. 7 4. Main results. 11 5. The integral over −G 0 as an integral over g. 16 6. The invariant integral over g as an integral over h. 17 7. An intertwining distribution in terms of orbital integrals on the symplectic space. 21 8. The special case for the pair O 2l , Sp 2l ′ (R). 32 9. The special case for the pair O 2l+1 , Sp 2l ′ (R), with 1 ≤ l ≤ l ′ . 35 10. The special case for the pair O 2l+1 , Sp 2l ′ (R) with l > l ′ . 37 11. The sketch of a computation of the wave front of Π ′ . 39 Appendix A. The Jacobian of the Cayley transform 40 Appendix B. Proof of formula (86) 41 Appendix C. The special functions P a,b and Q a,b 43 Appendix D. The covering G → G 49 References 52Let W be a finite dimensional vector space over R equipped with a non-degenerate symplectic form •, • and let Sp(W) denote the corresponding symplectic group. Write