The Burton arrangement I have is entitled “Larghetto” and yes, it is the Laschia ch’io pianga aria from “Rinaldo.” It’s in the key of C (or Cb on the pedal harp) and is two pages. Rhett’s arrangement is also two pages and is in the key of D (or Db on pedal). Both are playable on either lever or pedal harp.
The form of the Burton arrangement is ABACA (almost like the song by Genesis!).
Rhett’s is ABAA(an octave higher)CABAA(8va).
This probably doesn’t make much sense; sorry. Each arrangement has all three themes/sections; you can repeat any section or take things up an octave however you prefer.
If you’d like, email me at email@example.com. I could give you my number and I’d be happy to play both versions over the phone for you.
Julie in Atlanta