Work on “Engine Room,” particularly from rehearsal letter A to C.  Remember that the 8th note stays constant (and, if it helps you to remember this, the 16th note remains constant too).  Therefore, the speed of everything never changes, just how many 8th notes/16th notes fit in a bar.  LISTEN TO AND PLAY ALONG WITH THE RECORDING.  This will be the most help to you.  This is the link: https://www.youtube.com/watch?v=o68WVknJbOM

Lastly, thanks for being willing to tackle these challenging pieces.  The Portraits in Rhythm etude was stretching (and yes, we’ll come back to that before the concert, so don’t worry about that!), and this piece is very challenging.  This is the kind of literature college musicians play, and it’s very impressive to see high schoolers your age able to tackle such weird rhythms and meter shifts.  Thank you for your work!