You can start by taking a look at the lick I've transcribed below. It starts at 2:54 into the song, and it is played over an Em7 groove. The chord scale for Em7 is E dorian, and that's also how the lick starts. In the first measure there are embellished A major and G major triads, both of which are contained in E dorian. In the next measure Chick Corea plays a purely pentatonic melody. However, it is not in E minor pentatonic but in F# minor. This is still inside because all notes the of F# minor pentatonic scale are contained in E dorian. On the second beat of the third measure, he moves to the G minor pentatonic scale. This is the outside part of the lick. He uses a chromatically ascending line to move back to E dorian, and he finishes by a lick taken from the B minor pentatonic scale, which is again totally inside because all notes of the B minor pentatonic scale are part of E dorian.
So why haven't I just transcribed the outside part of the lick, i.e. the G minor pentatonic part? Because I believe that the art of playing outside lies not only in the choice of the outside notes but also in the way you move outside and back inside again. So let's have a look at these 3 components and how Chick Corea made his choices:
- moving outside: by moving down a half-step, which takes him from F# minor pentatonic to Gm pentatonic. Note that he does not move up, even though the scales move up from F# to G!
- playing outside: he uses the G minor pentatonic scale, which contains 3 outside notes (Bb, C, and F) and two inside notes (G and D). It is important to connect the outside notes in some 'logical' and musical way, and using the familiar pentatonic scale is one great way of doing this.
- moving back inside: he plays a chromatically ascending run which adds a lot of tension before it resolves back to E, the root of the tonality. From there he stays inside by playing another pentatonic lick.