Overview – The guitar is set up so that you can play 6th and 3rd double-stops easily. These 6th and 3rd double-notes are often moved horizontally, and often using sliding notes. The sound of sliding 6ths and 3rds is a sound closely associated with guitar, and no other instrument. It’s one of the guitar’s most distinctive sounds.
Right Hand – If you’re using a pick, playing 6ths is the one hybrid-picking technique you must learn, even if you don’t learn any other hybrid-picking techniques. That’s because 6ths runs are played on two non-adjacent strings, so there’s a muted string in between. An alternative technique is to pick across 3 strings, muting the middle string. It’s more common on electric guitar, and it doesn’t sound as clean as hybrid picking. In these examples, I’m using middle finger to pick the higher string. You can use the same hybrid technique for playing 3rds, or you can pick two adjacent strings.
Sixths in C
This horizontal scale movement can be crossed from the D and B strings over to the G and High E strings. That moves the harmonized 6th scale from the key of C up to the key of F.
Sixths in F
For each 6th interval on the G and High E strings, there is a corresponding 3rd interval in the same key. You get the 3rd interval by moving the note on the High E string over the B string. The diagram below shows the corresponding 3rd intervals.
If you combine the notes on all three strings, you get major and minor chord triads.
