A single-input modal control theory is developed whereby the loop gains of a single-input time-invariant multi-variable system may be calculated using simple formulae for the cases when both the open-loop plant matrix and the closed-loop plant matrix have a number of sets of distinct and confluent eigenvalues. The results may be applied in a sequential manner for multi-input systems with repeated sets of confluent eigenvalues provided that the appropriate mode-controllability conditions are satisfied. A number of illustrative examples are included.