Evolution of the νHF vibrational-rotational band in an HF/CO mixture is studied at CO density successively increasing from a dilute gas to condensed system. By using super-Lorentzian contours, the vibrational-rotational band of free HF molecules was calculated for the density ranging from 15 to 310 Amagat, and, by separating the bands, the shape of the band of bound molecules, which comprises the νHF bands in the OC...HF and CO...HF complexes, was determined. The relative intensity of these bands was found to be 2.3. By using a nonempirical potential within the context of an approximate separation of the radial and angular motions, the energies of vibrational-rotational states were computed, as well as the frequencies of transitions between them, which were used for calculating the vibrational-rotational absorption band of the isolated OC...HF complex. With the spectral exchange effects taken into account in terms of the model of strong collisions, the variation of the band shape of the OC...HF complex on increasing the system density was calculated. Parameters of the band of the weaker CO...HF complex were measured, and its enthalpy ΔH2 = -770 cm-1 was found from estimation of its energy.