A hammer-on always raises the pitch of the note that is being played. As with all slurred notes, only the first note in the pair is actually
played with the right hand. Notes are usually played by fretting at a certain position and then playing a string, but with the hammer-on the procedure is reversed. First you
play the open string, then you hammer down on a fret to produce a second tone. You can also begin with a fretted string, and then hammer down on a higher fret of the same
string with your 2nd, 3rd, or 4th finger.
In the exercise that follows, hold your index finger down on the 2nd string 2nd fret, then use the middle finger of
your left hand to hammer down on the 2nd string 3rd fret.