has anyone ever listened to a 45lp at 33.3

Try listening to the Nat King Cole analogue production reissues at 33 rpm. It sounds like Barry White on steroids! The first time I put the LP on I forgot to change the speed to 45 rpm. It scared me to death when he started singing.

I did this with a Radiohead EP I bought at a used record store. I assumed it was an LP I had never heard of and played it twice at 33 rpm, all the while thinking it was one of Radiohead's "experiments". Then I read the label and saw it's a 45. Of course it sounds a lot more like RH when played at the correct speed.

For a truly mind-blowing experience, try listening without smoking pot.

When Reference Recordings issued a 45 rpm recording of Respigi's "Church Windows" a critic actually made the mistake of listening to it at 33 1/3 rpm. The amazing thing is that the critic actually acknowledged the mistake in a subsequent report (the piece is not an often heard warhorse). It is easier to be fooled and not recognize such a mistake with non-vocal classical pieces than most other kinds of music.

There was a 45 back in the 60's called "The Martian Hop". I was about 7 or 8 when in came out. I still remember my brother playing at 33rpm and figuring out it was meant to be that way. Sped up and it sounded like a cheapo sci-fi martian.
-John