It caught my attention too, and a few years back I was lucky enough to put this question to producer Owen Morris. 


Is the clip of Noel singing Morning Glory at the start of Acquiesce from a demo of that song, or was it specially recorded for Acquiesce?
Owen Morris: "I gotta think about this. Noel played me acoustic versions of tunes like Morning Glory on the Some Might say/Acquiese session. But as far as I can remember, it was probably on a pass through the tape hone I was setting Noel up to either do his vocals or play tambourine.....and he would've sang/played that little snippet of Morning Glory as a cheeky reference, specifically to get fans like you asking about it in later years. We'd have listened back to it, laughed at it, and Noel would've said to leave it on."


I'm not sure if Noel has ever spoken about this in an interview though. The snippet of Wonderwall on Hello is from when they were trying to record Noel playing acoustically on top of a wall outside Rockfield Studios. Noel spoke about this in an interview printed alongside Select magazine's original review of Morning Glory.

Great interview. Still curious who the mystery producer is though.