Check out the very funny comedy "Everybody Does It" co-starring Holm, Paul Douglas (original Broadway Harry Brock from "Born Yesterday") and Linda Darnell. Holm plays a woman with classical music aspirations who isn't very good; her husband somehow, unbeknownst to her for a while, turns out to have a helluva fabulous voice and is pursued by Linda Darnell for the opera. Holm supposedly tried to make her voice mediocre or worse for the role, and I'm sorry to say, it's not that much different from when she was singing ballads in "Bloomer Girl" (ok, maybe a little). She's wonderful in more charactery stuff like Ado Annie, and she was a very fine actress. But doing the majority of the singing in "King and I", though it is written for a fairly limited range, might have been a challenge -- at least the lyrical "Hello, Young Lovers". She'd have acted "Annie Get Your Gun" very well again, but Ado Annie in "Oklahoma!" only has 2 songs while Annie Oakley sings most of the score. I don't think she'd be up to it, so I agree with larry13. Nellie is written fairly easily for the voice, so she'd probably have been fine.