Unique chord, or uniqueish?

I've played a lot of chords over the past 50 years, but there's one I only recall playing in one particular song.

I'd love to be told it is also found in other songs, but I don't remember it occurring, so far.

Thirteenths are among my most favourite chords, but while they are not ubiquitous, you do encounter them with some degree of regularity.

But where else does the great chord at the beginning of the second bar of The Sound of Music also occur?
[clears throat] The hills are alive with the sound of
mu -sic.

That chord on the mu is one weird chord. You play an E major first inversion chord with your right hand, and a low F with your left. It sounds amazing.

Any takers?