Raman scattering measurements have been performed on semiconductor-insulator nanocomposites in which the semiconducting phase occupies a significant (30%) volume fraction. The composites have been synthesized by high pressure injection of the conducting melt into the nanochannels of commercially available insulating matrices. The optical phonon spectra of GaSb- and Te-SiO2 composites exhibit shifts, broadenings, and asymmetries when compared to those of the semiconducting bulk. These are interpreted in terms of strains and phonon confinement in the microcrystalline semiconducting phase. Xray diffraction measurements allow us to correlate the effects of crystallite size and strains on the optical modes of the composites.