Lattice frequency spectra of Pb and Pb40Tl60 have been measured at 90 °K by inelastic coherent scattering of slow neutrons from a polycrystalline specimen. The results compare favorably with the tunneling measurements of Rowell, McMillan, and Feldman. In Pb40Tl60 we see direct evidence of energy smearing arising from the finite lifetimes of the phonons caused by force-constant disorder in the alloy.