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##
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## 8. Apparatus as in claim 7 further comprising: initializing means for producing initial values for P.sub.o (A.sub.ij) the transition probabilities and for P.sub.o (F.sub.2 (l).vertline.A.sub.ij) the label output probabilities; and deleted estimation processor means for linear averaging the re-parameterized label output probabilities received as input from said re-parameterizing means against the initial label output probabilities received as input from the initializing means, given the label outputs generated by the acoustic processor means in response to the subsequent speaker uttering said part of the sample text, to produce smoothed label output probabilities P.sub.s (F.sub.2 (l).vertline.A.sub.ij) which have a smoothed probability distribution.