  A mixed-symmetry nuclear shell-model scheme for carrying out calculations in
regimes where there is a competition between two or more modes is proposed. A
one-dimensional toy model is used to demonstrate the concept. The theory is
then applied to $^{24}Mg$ and $^{44}Ti$. For lower pf-shell nuclei such as
$^{44-48}Ti$ and $^{48}Cr$ there is strong SU(3) symmetry breaking due to the
spin-orbit interaction. However, the quadrupole collectivity as measured by
B(E2) transition strengths in the yrast band remain high even though SU(3)
appears to be broken. Some results for the so-called X(5) symmetry that falls
along the U(5) $\leftrightarrow$ SU(3) leg of the Interacting Boson Model are
also considered. The results show that the mixed-symmetry concept is effective,
even when strong symmetry breaking occurs.
