Beat‐frequency light generation in ammonium dihydrogen phosphate, arising from interaction of 3470‐Å ruby maser second harmonic and 7454‐Å ruby stimulated Raman scattering from benzene, has been investigated. A single crystal can serve to efficiently produce both the ruby second harmonic and the beat note, since in each process the phase matching condition is satisfied at nearly the same crystal orientation. The phase matching effect is readily observable when the crystal is rotated.