Adding B String Notes to Shell Voicings - Part 1: Major II-V-I
Once you have the basic shell voicing shapes under your fingers and are comfortable using them across the neck, a great next step is to start adding the B string to your voicings to expand the sound. Using a little bit of music theory as a guide will allow you to employ the B string in a thoughtful and creative way.
In our previous shell voicing lessons, all of the voicings we’ve used have contained only the root, third and 7th of the given chord. By adding notes on the B string to our three-note shell voicings, we can introduce either the 5th or the 9th to each chord, creating a fuller sound, and utilizing more of the fretboard.
While this lesson will focus on adding only the 5th and 9th to basic shell voicings. The B string can also provide 3rds, 11ths, and 13ths, which we will cover in later lessons.
We’ll start with the II-V-I pattern #1 and add B string notes on the same fret as the roots. 
Notice that when the root of the chord is on the A string, the added note ends up being the 9th. If the root is on the E string, the added note will end up being the 5th of the chord. Here is the result of adding the same note to the II-V-I pattern #2: 
There are many jazz standards and common song forms which can be used to practice these new voicings. It is important to note that some songs will include chords with “flat five” (b5) or “flat nine” (b9) in the symbol, as well as the occasional “augmented” (+) or “sharp five” (#5) and “sharp nine” (#9). When these chords occur you’ll want to adjust the 9th and/or 5th to match the chord symbol.
Now that the natural 5th and 9th have been introduced to our basic chord voicings. It is time to look at the “minor 7th b5,” as well as the “dominant 7th b9” chord as they are two of the most commonly encountered chords in jazz standards.