Watch the Side Slippin’ online guitar lesson by James Hogan from 50 Jazz Rock Licks You MUST Know
This lick is a cheap and easy way to incorporate some "outside" sounds into your playing. I once heard a famous tenor saxophonist refer to this concept as "Poor Man’s" outside playing, but it certainly gets the job done and is extremely effective when not overused. You’ll hear this from time to time in the playing of John Scofield, Mike Stern and countless others. I first heard it on a Woody Shaw record.
Basically, we’re taking a stock E minor pentatonic sequence here and combining it with an F minor pentatonic scale which is 1/2 step higher. When you play a minor pentatonic scale up a half step from the key like this you get all of the altered intervals! (b5, #5, b9,#9) When "side slipped" back to the parent key you get lots of tension and release."