This is a basic introduction to metric modulation from 4 to 3. By playing a 4 note pattern (1-2-3-5) over a triplet, you imply a new tempo. This is a great way to add tension and interest in your improvising. Each pattern starts in eight notes, then is played note for note in the triplet. I’ve put accents over the notes in the triplet. It’s important that you learn to feel the pattern of 4 in the triplet, so adhere to the accents. I would start at a slow tempo (about quarter note + 60), so you can line up the notes in the triplet pattern.
Be very aware of how and where each accent lines up with which beats. The aim here is to be able to feel two different tempos simultaneously. The scale pattern is built from the jazz minor (ascending melodic minor), and I’ve written this exercise in only the first six keys around the circle of 5ths. You can of course transpose this into all keys, and/or any other scale or melodic pattern you like. If you’d like to study this type of polyrhythm in a methodical, thorough and practical way, please consider my eBook, Rhythmic Dissonance: Exercises to Improve Time, Feel and Conception.