It's well known that the $A_{n-1}$ Macdonald polynomial $P_\lambda(x;q,t)$ becomes the Schur function when $q=t$. Schur functions are characters of the general linear groups. What about other Macdonald polynomials (at least associated to the non-exceptional root systems) in that specialisation of parameters? I cannot find a reference which contains such information.
Thanks in advance.