I love the Corelli variations. It's a fantastic set, although it definitely has its brutal moments for the performer... Here's what I found to be the most challenging:
- Var. XX - Staying relaxed through all the leaping octaves! I practiced these a lot... slow practice really helped, as did playing only what falls on the main beats, then adding in the inner notes.
Var. XVII - Maintaining a connected, singing line in the right hand. Those long notes die away so quickly... it's important to listen to the end of each note and how it connects to the beginning of the next note.
Var XIII - Memorizing all the chord changes in this variation. Brutal. All the subtle differences in chord quality give this variation its dark, prickly atmosphere... some careful voicing of the inner lines in strategic spots can really highlight the harmonic language here.
Var. XI - Bringing out the accents in this variation. If you emphasize the accents where Rachmaninoff has written them, it really helps with staying relaxed in unaccented spots.
Var. X. Everything.... it's just hard. Lots of slow practice, lots of practicing in groups...
Var. VII. Stamina. I always found this variation to be tricky. I was never quite happy with the fingering I was using.
Var. II - Memory! This one is confusing. I copied it out on manuscript paper to help me remember it better.
All the best! This is such a masterpiece. Have you seen Ashkenazy's video about them? Super interesting...https://www.youtube.com/watch?v=xEHh84Ptvaw