YOU are not the ONLY one on stage! Your pianist is your team mate. She has worked just as hard as you have to learn your music. She also much be constantly aware of what nuances you bring to a piece of music. There is a real art to being an accompanist, and not all pianists can do it.
There is also an art to knowing how to rehearse with your accompanist. As the soloist, you need to be ready to communicate various details to you accompanist:
- You must set the tempo.
- You are not a metronome, and shouldn't play like one. Music ebbs and flows, and you need to know where you want to speed up or slow down.
- Are there places where you just need a fraction more time to get through the notes? This must be addressed, too.
- You need a clear idea of where you are going to take a breath in passages without rests.
- Dynamics! How loud, how soft, when do you start your crescendo? Are there places where it changes suddenly?
In addition to all of this, there is one more step you need to take: familiarize yourself with the piano part. Don't just listen to it, but sit down with the score and read it through. I wish I could take credit for this final thought, but I can't. I have a recital in 2 days, and my accompanist just said this:
"Music is a conversation between the flute and the piano. Analyze the score so you can understand when each instrument is talking."