It's all the more remarkable considering that both Marsh and fellow saxophonist Ted Brown play this composition on tenor saxophone, a real workout of the horn's altissimo range.
I've also decided to take a crack at Milestones, a composition written by either Miles Davis or John Lewis, depending on which source you believe. While original credit for the composition went to Charlie Parker, almost every contemporary source disagrees with this. But whether the actual author was Miles Davis or John Lewis remains a matter of some dispute, even among prominent writers. Feather (1949, p. 18), Yanow (2000, p. 76), Koch (1988, p. 103) and Tingen (2001, p. 29) credit Davis, while Giddins (1998, p. 340), Priestly (2005, p. 59), and Szwed (2002, p. 60) credit Lewis. Giddins includes elaborate anecdotal information about the recording session, and asserts that the tune was written "as a gift" from Lewis to Davis. So until I hear a compelling contradiction to this story, I'll go with Lewis as the author of Milestones.