7. Apparatus as in claim 6 wherein said expanding means includes: means for calculating a transition probability P(A.sub.ij) in response to a transition count input; forward-backward processor means for iteratively producing transition counts count.sub.n+1 (A.sub.ij) and label output counts count.sub.n+1 (F.sub.2 (l), A.sub.ij) in response to a transition probability input P.sub.n (A.sub.ij), a previously calculated label output probability P.sub.n (F.sub.2 (l).vertline.A.sub.ij), and labels generated in response to the subsequent speaker uttering said part of the sample text; entry update calculator means for computing a value P.sub.n+1 (F.sub.2 (l).vertline.F.sub.1 (k)) in response to receiving as input (i) a previous entry value P.sub.n (F.sub.2 (l).vertline.F.sub.1 (k)), (ii) label output probabilities for the reference speaker P(F.sub.1 (k).vertline.A.sub.ij), (iii) the most recent label output count count.sub.n+1 (F.sub.2 (l), A.sub.ij) from the forward-backward processor means, and (iv) a previous label output probability value P.sub.n (F.sub.2 (l).vertline.A.sub.ij); and calculator means for computing updated re-parameterized label output probabilities ##EQU19##
6. Apparatus as in claim 5 wherein said re-parameterizing means includes: means for computing a respective probability value P[F.sub.2 (l).vertline.F.sub.1 (k)] for each entry in a confusion matrix indicative of the probability of the lth label as spoken by the subsequent speaker corresponding to the kth label as spoken by the reference speaker; means for storing the values for the confusion matrix entries; means for expanding each label output probability of the subsequent speaker P[F.sub.2 (l).vertline.A.sub.ij ] in terms of confusion matrix entry values and label output probabilities for the reference speaker as: ##EQU18## where N is the number of labels in the alphabet of labels.