  Relevance of the M\"ossbauer spectroscopy in the study of harmonically
modulated electronic structures i.e. spin-density waves (SDWs) and
charge-density waves (CDWs) is presented and discussed. First, the effect of
various parameters pertinent to the SDWs and CDWs is outlined on simulated
119Sn spectra and distributions of the hyperfine field and the isomer shift.
Next, various examples of the 119Sn spectra measured on single-crystals and
polycrystalline samples of Cr and Cr-V are reviewed.
