Laser-ablated beryllium atoms have been reacted with hydrogen cyanide ((HCN)-C-12, (HCN)-C-13, and (DCN)-C-12) during condensation in excess argon at 6-7 K. In the matrix infrared spectrum, the major products observed are BeNC, BeCN, HBeNC, and HBeCN. Consistent with typical beryllium bonding, these new beryllium species are linear molecules. Density functional theory calculations on these products with the BP86 functional and 6-311G* basis sets predict vibrational frequencies extremely well, even for HBeCN where mixing between the neatly isoenergetic Be-H and C=N stretching modes causes significant complications in the spectra. Although B3LYP and MP2 calculations are more sophisticated than the BP86 method, they do not predict the vibrational frequencies of these products nearly as well. More important is the carbon 12/13 isotopic frequency ratio as a description of the normal modes, and the BP86 method generates 12/13 ratios much closer to observed values for HBeCN than frequency ratios from the more time-consuming CISD method.