Here's one example of a very simple keyboard improvisation using notes of the E minor pentatonic scale in the RH. Perfect 5ths in the E and D position accompany in the LH.

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1) Let your LH play a perfect 5th in the E position.
2) While you're sustaining those notes, let your RH make melodies by playing any notes of the E minor pentatonic scale.
3) When the LH notes fade, play and sustain them again.
4) Keep it simple!
5) Yet, if you'd like a change of pace from the sound of the LH, simply move it down a 2nd to a perfect 5th in the D position.
Notice how the exact same RH melody notes E,G,A,B,D sound different when played against these different LH notes.