The pentatonic A minor riff improvisations apply the same rhythmic profile to strings of pentatonic scale tones which go further up the keyboard than the main riff, with more of an ‘ambling about’ feel.
Listen to the on-page audio of both improvisations as you read the second page of MS until you’re familiar with the music. The improvisations are not repeated. The performance recaps some of the original music before an unscripted ending.
Improvisation 1 is has the same 5-m7 lead-in as the main riff. See if you can get Improvisation 1 from just the audio file (first half).
The MidiPiano performance takes you through the build-up of syncopation as before. Note that the 5-m7 lead-in figures are all anticipated and all in unison.
Improvisation 2 goes up a full two octaves and is a lot more varied rhythmically.
Here is the 'bare bones' pentatonic scale-tone string.
See if you can get the second improvisation from just the audio file (second half). For more help, watch the MidiPiano performance and pick out the sections you need to practice.
You can use the A minor pentatonic riff pattern as a recipe for your own improvisations. Go on to ‘PRAM in D minor’ (PD 21-07-15) for more spontaneous variations on the A minor riff material which demonstrate some tricks and techniques.