The Extended Karplus-Strong (EKS) algorithm  extends the KS digitar in a number of ways that will be introduced one-by-one and then brought together in the complete program listing shown in Figures 9 and 10. The EKS extensions were motivated by the demands of a musical composition7and the interpretation of the KS algorithm as a transfer-function model of a simplified physical string [11, pp. 158-198]. They illustrate how several small digital filters can achieve various desired musical effects. We will see that the EKS can be regarded as a blend of spectral and physical (transfer-function) modeling techniques.
Figure 4 illustrates where the various filters may be located in the patch. The filters in series outside the feedback loop can of course be implemented in any order, and the filters within the feedback loop can be arbitrarily reordered. (The series order of linear, time-invariant filters may matter in fixed-point, but generally not in floating-point.)