Bill Bubble Guy said:
Also I wonder since Frank and Jim were always more or less set to play Ernie and Bert as minor muppetz posted earlier, how then would Bert's voice have differed?
After all Bert as we have always known and loved him basically has the "Fozzie-ish" voice
They might have had the same voice. Another voice Frank could have used for Big Bird (which I think is just slightly different) that would have been appropiate (for first season Big Bird, anyway) would have been Harvey Kneeslapper's voice.
If Jim Henson performed Big Bird then I think he would have had Big Bird sound like either Kermit and Ernie or Link Hogthrob. Link's voice would have been appropiate for the first season, but I am thinking that the Ernie voice also would have fit even though Big Bird was dumber back then (Enie kind of sounded a bit more like a hillbilly in earlier sketches like Rubber Duckie).
In fact, according to the book The Story of Jim Henson: Creator of the Muppets, Big Bird was originally built with Jim Henson in mind to perform Big Bird. However, Kermit Love didn't think Jim Henson was walking like a bird was supposed to walk when Jim tried the outfit on, and then Jim decided that walking like a bird wasn't his style of walking.