Many of the older keyboards, of which yours is one, tended to be velocity sensitive but still had only a single sample so velocity was translated into volume more than anything else. As a result, you got a sudden attack that did not correspond to a very soft touch. Modern digital pianos seem to have resolved this problem.What one does lose, however, is (in general) color. Since you are restricted to producing sounds based upon the samples, you can never get a sound outside the range of the sample and the filter that is applied to that sample. For most amateur pianists this problem can range from "problem, I don't have a problem" to "that's pretty annoying."