If $\lambda,\mu$ are two dominant weights for a Lie group $G$, then there is a canonical (up to scale, perhaps) surjection $V_\lambda \otimes V_\mu \to V_{\lambda+\mu}$ of finite-dimensional representations, which I have occasionally heard called the "Cartan projection".

To each irreducible (or standard) Harish-Chandra module for $({\mathfrak g},K)$, one can associate a $K$-orbit on $G/B$. For finite-dimensional representations, this orbit is the open $K$-orbit.

I want to know what analogues exist of the Cartan projection out of $V\otimes W$ if $V,W$ are two Harish-Chandra modules with the same associated $K$-orbit (other than the open orbit case above).

The answer may be something like "every H-C quotient of $V\otimes W$ has the wrong Gel$'$fand-Kirillov dimension for it to again have that associated $K$-orbit," in which case I'd appreciate references that make that most clear. (I will be sad, but not overly surprised, if that is the case.)