When it comes to playing intervals on the guitar, people often favor thirds, sixths, fifths, and even fourths. But many people find sevenths harmonically too dissonant to use. Not me. I love sevenths. I think major and minor sevenths are beautiful and I improvise with them all the time. A great way to get a handle on sevenths is to start with the four-string C major scale in Ex. 1 (which is also an A natural minor scale). Once you’re familiar with this scale fingering, harmonize it diatonically using sevenths, which will result in the sequence of major and minor sevenths shown in Ex. 2. These grips sound good over, say, a Cmaj7 or Am7 chord.
Once you’ve memorized this harmonization of the scale, you’ll be able bounce around comfortably from seventh to seventh. And guess what? Memorizing it is easier than you might think, because check it out: If you know the first three sevenths (each of which takes place on the sixth and fourth strings), you simply repeat those same shapes on the fifth and third strings. That’s six grips for the price of three!
Similarly, you may notice, the sevenths on the fourth and second strings are identical in shape and fret position to those on the third and first strings. Any seventh you play on the fourth and second strings can easily be answered with another seventh of the same shape on the third and first strings [Ex. 3]. (Notice that this conveniently holds true up in the fourteenth position, too.) Also, be sure to try variations, such as playing the sevenths melodically [Ex. 4] or in another key, such as D minor. With a Dm9 chord as our backdrop, the shapes now project the D Dorian mode [Ex. 5].