The hexatonic scale sounds slightly more melodic than the pentatonic scale. The addition of the second interval helps smooth the distances between the notes. Most melodies that are sung contain small intervals between the notes. Melodies that are termed “lyrical” are based on close intervals. The pentatonic scale has some large jumps between the notes that can make it hard to be lyrical. When you play the hexatonic scale, the added note helps smooth out the scale and makes it more melodic. To hear a master of the pentatonic and hexatonic scales, listen to Eric Johnson's “Cliffs of Dover.”
If you don't have total command of the fingerboard, adding the second interval to the F-minor pentatonic is easier said than done. You may want to go back to your charts and add the note. Since the five forms of pentatonic are in the key of F, you should try to make those forms into hexatonic scales. The interval of a second when applied to F is the note G. Just add two frets to the root to find the second. Go back through every form and add that note to each shape. Use the fingerboard chart in FIGURE 5-2 to help you find all the Gs.
You'll discover that certain forms work better for hexatonic than others. If you'd like to adapt your own scales, you'll find that neck paper is the single most helpful tool for working scales out. Being able to see the entire neck is crucial to playing the scale fully. If you stumble upon a “happy accident” note, try to work it out all over the neck. Neck paper is available at most music stores. In a pinch, get a ruler and draw your own.