Rascher performed the original Dahl about 14 times, and some of those live performances were archive recorded. None were commercially released (except a late one from a Pennsylvania music festival). I have a few of his live recordings. His playing is superb, but the overall performances of the piece are wanting, in that the ensembles were still grappling with music of unusual demands and sophistication. In giving me these performances Rascher gave me permission to play them for any who were interested in either my classes or my lectures or in private visits (tantamount to an uninvited lecture during the visit), but requested that they not be copied. If, after Covid, you wish to learn more and hear Rascher's remarkable performances, let me know. This can also be accomplished through Zoom these days.
I can also send you a representative version of my own live performance, and my commercial recording should be coming out this year. But do understand that the original is very very different than the revised, published version that everyone has.