Bass players grab the perfect 5th interval all the time—it lies right under the fingers, and it’s probably the most commonly used double-stop on the bass. You can find the perfect 5th by playing any major, minor, or dominant scale from the 1st note (the root or 1) up to the 5th note (the 5).
Ex. 1 demonstrates a typical double-stop bass line using the 5th over a C minor chord progression. Use this thick and heavy sound when you need a lot of bottom—you know, when the sax player turns toward the drummer, starts to get red in the face, and does that little dance.
Intervals of major and minor 3rds are very melodic (Ex. 2). Be careful—3rds can sound muddy, so these are handle-with-care double-stops. If you drop the bottom note of this exercise one octave, as in Ex. 3, you are playing a 10th interval. These double-stops bring out the beautiful sonority of the bass, and you can use them to describe the most important quality of a chord: whether it’s major or minor.
Use the suggested fingerings, but here’s a trick: I often play both notes of the minor-10th double-stop with just my 1st finger by using a barre technique. I play the A on the E string with the tip of my index finger and simultaneously play the C on the G string with the back part of my index finger near the knuckle.
Next time we’ll continue with double-stops by getting funky—and by Taking a Walk on the Wild Side.