I've done those shell voicings quite a bit on the bass guitar, where the number of notes available for chords is limited (four strings, usually, and the bottom two strings aren't really useful unless you're playing above the 12th fret). What's interesting (and convenient) is that if you play a shell tritone on the I chord (third & minor 7th), you only have to take the two notes down a half-step and you've got the shell voicing for the IV chord (minor 7th and third).

--Doug


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