Time-varying system parameters and control inputs are assumed constant over small intervals of time and corresponding incremental time transition matrices are determined from l-invariant system theory. A sequence of incremental convolution operations determining incremental state responses yields the overall-time state response in a discretized form, and is shown to correspond to the continuous integral-convolution response equation from analytical theory. The incremental time response synthesis is extended to a derivation of Neumann's Series and discrepancies relevant to numerical work are noted. At appropriate stages in the development results obtained from high order transition matrices are related to those of the first order finite difference method. The graphical approach elucidates problem structure and contributes to a clearer understanding of lvarying system analysis for the benefit of both tutorial and practical numerical work on non-singular systems.