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This is a stompin', bluegrass-fiddle-style riff that's perfect for your next hoe-down! It involves the use of ringing double-stops on the top two strings and an open drone note (the open G string), which is picked/strummed along with some of the fretted notes and allowed to ring thoughout most of the phrase.
The riff is played as if it were in the key of G, but I'm using a capo at the second fret to transpose everything up two frets and one whole step, to the key of A, which sounds brighter and more fiddle-like in this context. There's a wide fret-hand stretch involved, and using the capo helps make that easier to perform, as the frets are now spaced closer together. If the stretch stills feels too arduous or painful for you to make in this position, try moving the capo up to an even higher position, which will further shorten the distance between the frets.
Barre your index finger across the top two strings at the third fret (relative to the capo), and use your middle finger and pinkie to reach the notes at the fifth and seventh frets. The fret-hand thumb should press against the back of the neck, right in the middle, where the D and G strings line up.
When you get to measure 4, release the index-finger barre and use the index and ring fingers to fret the notes on the B string's third and fifth frets.
Throughout the riff, take care not to inadvertently mute the open G string with the tips of the fret-hand fingers. The strumming should be loose, relaxed and "in the groove." Be sure to use the pick strokes indicated.
The tempo is 130 beats per minute, 88 for slow practice.