Preface to the series. Introduction. 1. Universal parameters in mixed crystals (I.P. Ipatova). 2. Phonon response theory and the infrared and Raman experiments (D.W. Taylor). 3. Effect of composition disorder on the electronic properties of semiconducting mixed crystals (A.L. Efros and M.E. Raikh). 4. Infrared and Raman studies of disordered magnetic insulators (W. Hayes and M.C.K. Wiltshire). 5. Spectroscopy of excitons in disordered molecular crystals (E.I. Rashba). 6. Phonon multimode spectra: biphonons and triphonons in crystals with defects (V.M. Agranovich and O.A. Dubovsky). Author index. Subject index. Materials index. Cumulative index.