Miriam Stafford's daughter, Julie Stafford Straton, kindly posted (02 Feb 2010) a link to a page with a recording of Miriam (with Rita Weill and Janet Smith) which, for convenience I repeat here:
http://www.folkways.si.edu/TrackDetails.aspx?itemid=32580

It takes you to a Smithsonian site where you can, if you wish, buy a recording or a track, and you can listen to a snippet of each track for free, thereby quickly and easily hearing Miriam's voice. What might be a little less obvious is that you can also download, for free, the liner notes for the recording, and in those liner notes there is more information, apparently written by Miriam herself, about her musical (and to some extent life) journey up to the point of that recording.