Is it reasonable to expect that an experienced cornet player should be able to pick up a "middle of the band" instrument, like a baritone, or an Eb horn and become reasonably proficient in a few hours across a day or two? 

How large is the shock to the embouchure and how costly is it to then move back?


Question: Noise canceling headphones make strange sound when I touch my MacBook Pro
Answer: It appears your wall socket is not properly grounded, which may cause electrical interference on your headphones when touching the MacBook Pro.

Have a look at this related answer on possible measures you can take to establish a proper electrical grounding.