Okay, we're going to take this whole matter of the Pippin commercial clearly into the realm of Way Too Much Information! But that's what blogs are for, right? Andrew Leal sent me this…
I read about the Pippin commercial info on your site, and decided to check using one of the best commercial info sources I've found, as far as from the grey-flannel suit's mouth: the Clio Awards archive. Their entry confirms beyond doubt that the voice is indeed Alexander Scourby. Here are the full credits from the spot as they have it listed, most of which just confirm the info you already have about Ash and LeDonne:
Dance :60 / Pippin
Blain Thompson, New York
Television/Cinema, Best, 1974Credits: Agency Producer(s): Peter Le Donne • Art Director(s): Morris Robbins • Client Supervisor(s): Stuart Ostrow • Composer(s): Stephen Schwartz • Copywriter(s): Peter Le Donne • Director(s): William Fucci • Editor(s): William Fucci • Performer/Voice: Ben Vereen, Pamela Sousa, Candy Brown, Alexander Scourby • Producer(s): William Fucci • Production Company: Fucci-Stone, New York • Scenic Designer(s): Carman D'Avino • Account Supervisor: Jeffrey Ash
I've found the Clio site to be an incredible resource and some of the revelations have been a surprise (everyone knows Gene Wilder voiced the stomach in the R. O. Blechman Alka-Seltzer spot, but I didn't know that the voices of the psychiatrist and the stomach's "owner" were supplied by Luis Van Rooten, a radio legend who worked on almost every coast at various times, sometimes shifting back and forth from week to week as demand arose, and was also heard in Disney's Cinderella as both the King and the Grand Duke.)
Okay, so that settles it: It was Alexander Scourby doing the voiceover. And if you've never seen the Alka-Seltzer spot Andrew mentions, it's this one. Thanks, Andrew.