Raman spectra of the nu(s)(dropC-H) stretching mode as well as Raman spectra in the lattice region of 15-200 cm(-1) of phenylacetylene (PA) dissolved in acetonitrile in frozen matrixes and liquid solutions as a function of concentration, temperature, and quenching rate have been recorded in the range of 77-293 K. The optical measurements were complemented by the differential scanning calorimetry (DSC) scans. The results reveal some dramatic changes with concentration, temperature, and quenching rate and are of potential relevance both to fundamental condensed phase modeling and to liquid crystal technology. We have discussed the origin of the vibrational substructure observed for the nu(s)(dropC-H) stretching mode of PA, and we have found that it represents stable and metastable crystal phases as well as nonequilibrium glassy crystal phases. Low temperature polymorphism in mixtures of PA in acetonitrile in the full concentration range has been characterized. We have found that the low temperature polymorphism of PA strongly depends on the concentration, temperature, and quenching rate.