A group spin approach is used to describe the interconversion of magnetization modes in systems of 3 equiv. spins 1/2. The most prominent effect of cross correlation of the fluctuations of chem. shift anisotropy and dipolar interactions is the transformation of 2-quantum coherences of 2nd rank into 3rd rank coherences. A novel expt. is described which allows one to observe such a process. [on SciFinder (R)]