Andy changed the time signature but kept the harmonic underlay. Clever. You have to listen carefully to catch what he did.
Since I was not a big Mendelssohn fan growing up (except Fingal’s Cave, which was used in a Warner Brothers cartoon which has now been “suppressed’ as it depicts a little African boy in traditional native garb brandishing a spear...Oh My!), I heard the JC Superstar version first. Then years later, I heard the violin concerto on classical radio and was stunned at the thievery! LOL!
Since I am a composer, I am VERY circumspect about copying other people’s melodies, even if they have been dead a long time.
Of course, there are only so many chord progressions, and only so many notes, so sometimes things happen inadvertantly.
But I would never do it deliberately like some of these guys seemed to have done.