A general formulation of the radiation force exerted on an object by a long wavelength sound field is developed in terms of an asymptotic multipole expansion. In various limits, the results of King [Proc. R. Soc. London, Ser. A 147, 212 (1934)], Gorkov [Sov. Phys. Dokl. 6, 773 (1962)], and Yosioka and Kawasima [Acustica 5, 167 (1955)] are recovered. In addition, the existence of a spectrum of monopole and dipole radiation force resonances is demonstrated which occur when the bulk modulus of the object is small compared to that of the surrounding medium. Near standing wave resonances, the bulk viscosity is shown to play an essential role in determining the force. For traveling waves, the bulk viscosity can lead to the dominant contribution to the radiation pressure even in the limit of zero frequency. For soap bubbles, the leading-order contribution to the radiation pressure is shown to be quadrupolar.