A stochastic theory of dye-matrix interaction is used to interpret inhomogeneous absorption lines and pressure effects on hole-burning spectra of free-base phthalocyanine doped into polymeric and rare gas matrices. It is shown that a realistic description can only be obtained if correlations between the matrix units are taken into account. Whereas the inhomogeneous absorption band can be reproduced correctly by inserting simple step-like dye-matrix and matrix-matrix correlation functions, more complicated forms are required to account for the hole-burning data. This leads to a possible new application of hole-burning spectroscopy, namely, the investigation of molecular arrangements on a nanoscopic scale.