New absolute stability results that unify and extend existing structured singular value bounds for mixed uncertainty are developed using frequency-domain arguments. These bounds generalize prior upper bounds for mixed-μ by permitting the treatment of non-diagonal real uncertain blocks, as well as accounting for internal matrix structure in the uncertainty. Several specializations to well known absolute stability criteria from the classical literature are given, which allow for a systematic comparison of these results in addressing the problem of robust stability for real parameter uncertainty.