Long wavelength ac bias record sensitivity is computed utilizing a model in which both longitudinal and vertical record fields are considered. It is assumed that the recorded magnetization is related by an anhysteretic susceptibility tensor to the signal field. At each depth in the tape the signal field is evaluated where the bias field amplitude is equal to the tape coercivity. Neither the effects of demagnetizing fields nor spreads in particle switching fields are included. The calculation yields excellent quantitative agreement with experimental sensitivity and correlates well with the shape of measured sensitivity vs. bias curves. The predictions of this model are compared in detail with those calculated utilizing solely longitudinal fields.