I've discovered that Rachmaninov must have really liked "Dies Irae." I've found it in three of his works now.
Back in May, I found it in his Symphonic Dances, Op. 45, although I never looked it up in the notation.
Last night, I found it in his Rhapsody on a Theme of Paganini, Op. 43. And then I found it in his Morceaux de Fantaisie, Op. 3 (it took me awhile to find it in the notation though). In the second movement (Prélude in C sharp), it's in the 7th to 9th measures:
(notation found
here)
He plays around with it more here than in the other two instances I've found, but it's still recognizable.
I'm sort of painfully out of my depth here, but it seems like he's taken "Dies Irae" and sort of inverted the notes and - after shortening the note values from the original - expanded his new note values in order to come up with the rhythmic motif that (with the exception of the Agitato section) he uses almost throughout the movement.
