Watch the Using 3rds and 7ths online guitar lesson by Christopher Woitach from Jazz Textures
When you strip a seventh chord down to it's essential elements, you're left with the two notes that describe the chord, the 3rd and the 7th. In this segment, we'll talk about using these crucial elements in progressions, and how to use them as a basis for creating other, more "colorful" voicings. I'll play some examples of moving through a progression using 3rds and 7ths, building new voicings, and moving through a progression using these new voicings.
Here's great exercise, play only the 3rds and 7ths of the chords in every tune you learn. Play them both as chords, and as single notes. Be careful to use strong voice leading, make sure that the chords are in the same register, and move smoothly from one to another. This will give you a firm foundation to work off of, to build new chords and lines from a more "clueful" perspective.